Virtual converged cable access platforms for hfc cable networks

ABSTRACT

A virtual converged cable access platform (CCAP) system and method for hybrid fiber CATV (HFC) cable networks. The system uses a new type of digital optical fiber node configured to receive optical fiber data packets, and reconstitute the optical data packets into RF waveforms suitable for injection into the system&#39;s CATV cable. The system replaces the legacy HFC head end with a simplified “virtual head end”. The system&#39;s virtual head end operates using a new type of virtual CCAP controller and virtual CCAP software that in turn controls high performance edge routers. Much of the intelligence of running the HFC cable system is managed by the controller software, while the edge router manages the interface between the CATV portion of the system and outside networks. The system can handle even legacy CATV RF signals by appropriate conversion operations, while reducing power and space needs, and improving operational flexibility.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT application PCT/US13/69760,“VIRTUAL CONVERGED CABLE ACCESS PLATFORMS FOR HFC CABLE NETWORKS”, filedNov. 12, 2013, inventor Shlomo Selim Rakib; this application also claimsthe priority benefit of U.S. provisional patent application 61/870,226“VIRTUAL HFC CONVERGED CABLE ACCESS PLATFORM”, inventor Shlomo SelimRakib, filed Aug. 26, 2013; this application is also a continuation inpart of U.S. patent application Ser. No. 13/674,936 “HYBRID ALL DIGITALFIBER TO CATV CABLE SYSTEM AND METHOD”, filed Nov. 12, 2012; thisapplication is also a continuation in part of U.S. patent applicationSer. No. 13/756,302 “METHOD OF TRANSFORMING HFC CATV ANALOG FIBERTRANSMISSION TO DIGITAL FIBER TRANSMISSION”, inventor Shlomo SelimRakib, filed Jan. 31, 2013; this application is also a continuation inpart of U.S. patent application Ser. No. 13/964,394 “HFC CABLE SYSTEMWITH ALTERNATIVE WIDEBAND COMMUNICATIONS PATHWAYS AND COAX DOMAINAMPLIFIER-REPEATERS”, inventor Shlomo Selim Rakib, filed Aug. 12, 2013;application Ser. No. 13/964,394 is also a continuation in part of U.S.patent application Ser. No. 13/346,709 “HFC CABLE SYSTEM WITH WIDEBANDCOMMUNICATIONS PATHWAYS AND COAX DOMAIN NODES, filed Jan. 9, 2012, nowU.S. Pat. No. 8,510,786; this application is also a continuation in partof U.S. patent application Ser. No. 13/555,170 “DISTRIBUTED CABLE MODEMTERMINATION SYSTEM WITH SOFTWARE RECONFIGURABLE MAC AND PHY CAPABILITY”,inventor Shlomo Selim Rakib, filed Jul. 22, 2012; and application Ser.No. 13/555,170 is also a continuation in part of U.S. patent applicationSer. No. 13/035,993 “METHOD OF CATV CABLE SAME-FREQUENCY TIME DIVISIONDUPLEX DATA TRANSMISSION”, inventor Shlomo Selim Rakib, filed Feb. 27,2011, now U.S. Pat. No. 8,365,237; application Ser. No. 13/555,170 alsoclaimed the priority benefit of U.S. provisional application 61/511,395“IMPROVED HYBRID FIBER CABLE SYSTEM AND METHOD”, inventor Shlomo SelimRakib, filed Jul. 25, 2011, now expired; this application is also acontinuation in part of U.S. patent application Ser. No. 13/400,415“METHODS OF ADAPTIVE CANCELLING AND SECONDARY COMMUNICATIONS CHANNELSFOR EXTENDED CAPABILITY HFC CABLE SYSTEMS”, inventor Shlomo Selim Rakib,filed Feb. 20, 2012; this application is also a continuation in part ofU.S. patent application Ser. No. 12/907,970 “HFC CABLE SYSTEM WITHSHADOW FIBER AND COAX FIBER TERMINALS”, inventor Shlomo Selim Rakib,filed Oct. 19, 2010; application 12/907,970 was a continuation in partof application 12/692,582 “Distributed Cable Modem Termination System”,inventor Shlomo Selim Rakib, filed Jan. 22, 2010, now U.S. Pat. No.8,311,412; application 12/907,970 also claimed the priority benefit ofU.S. provisional application 61/385,125 “IMPROVED HYBRID FIBER CABLESYSTEM AND METHOD”, inventor Shlomo Selim Rakib, filed Sep. 21, 2010,now expired; this application is also a continuation in part of U.S.patent application Ser. No. 13/478,461 “EFFICIENT BANDWIDTH UTILIZATIONMETHODS FOR CATV DOCSIS CHANNELS AND OTHER APPLICATIONS”, inventorShlomo Selim Rakib, filed May 23, 2012; U.S. patent application Ser. No.13/478,461 claimed the priority benefit of U.S. provisional application61/622,132 “EFFICIENT BANDWIDTH UTILIZATION METHODS FOR CATV DOCSISCHANNELS AND OTHER APPLICATIONS”, inventor Shlomo Selim Rakib, filedApr. 10, 2012, now expired; the contents of all of these applicationsare incorporated in their entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is in the field of hybrid optical fiber and CATV cablecommunications systems and methods.

2. Description of the Related Art

Cable television (CATV), originally introduced in the late 1940's as away to transmit television signals by coaxial cables to houses in areasof poor reception, has over the years been modified and extended toenable the cable medium to transport a growing number of different typesof digital data, including both digital television and broadbandInternet data.

Over the years, this 1940's and 1950's era system has been extended toprovide more and more functionality. In recent years, the CATV systemhas been extended by the use of optical fibers to handle much of theload of transmitting data from the many different CATV cables handlinglocal neighborhoods, and the cable head or operator of the system. Herethe data will often be transmitted for long distances using opticalfiber, and the optical (usually infrared light) signals then transformedto the radiofrequency (RF) signals used to communicate over CATV cable(usually in the 5 MHz to 1-GHz frequencies) by many local optical fibernodes. Such systems are often referred to as hybrid fiber cable systems,or HFC systems. The complex electronics that are used by the cableoperator to inject signals (e.g. data) into the system, as well asextract signals (e.g. data) from the system are often referred to asCable Modem Termination Systems or CMTS systems.

A more detailed discussion of prior art in this field can be found inU.S. Pat. No. 8,311,412, the contents of which are incorporated hereinby reference.

Prior art work with various types of CMTS systems and fiber nodesincludes Liva et. al., U.S. Pat. No. 7,149,223; Sucharczuk et. al. USpatent application 2007/0189770; Sawyer et. al., US patent application2003/0066087; and Amit, U.S. Pat. No. 7,197,045.

U.S. patent application Ser. No. 12/692,582, now (U.S. Pat. No.8,311,412) taught the advantages of producing a new type of opticalfiber node, there called a Cable Modem Remote Termination System (CMRTS)device, which essentially pushed much of the functionality (such asgenerating QAM signals) of the prior art Cable Modem Termination Systems(CMTS) from the central cable head down to many distributed opticalfiber nodes servicing neighborhood CATV cables

Motorola, in February 2012, proposed a non-virtual “Converged CableAccess Platform” (CCAP). This is exemplified in their February 2012publication CCAP 101: Guide to Understanding the Converged Cable AccessPlatform. As they discussed, “With consumers demanding more content onmore screens, cable operators are seeking a cost-effective strategy formigrating from conventional MPEG-based video delivery to IP videotransport. The Converged Cable Access Platform (CCAP) was designed withthis goal in mind, and proposes to combine data and video delivery as afirst step on the migration path. While cable operators today implementdata and video QAMs on separately managed and controlled platforms, CCAPprovides a blueprint for combining CMTS and edge QAM functionality inone hardware solution. CCAP promises significant improvements in QAMchannel density, and the flexibility for cable operators to expand dataand video services while also planning for a future world of all-IPdelivery.”

Other recent work on Converged Cable Access Platforms includes the Cablelabs Specification for Data-Over-Cable Service Interface SpecificationsConverged Cable Access Platform Converged Cable Access PlatformArchitecture Technical Report CM-TR-CCAP-V03-120511, released May 11,2012.

Juniper Networks MX 3D Universal Edge routers were described in JuniperNetworks datasheet 1000208-006-EN April 2010, “MX Series 3D UniversalEdge Routers”.

BRIEF SUMMARY OF THE INVENTION

The present disclosure teaches a virtual converged cable access platform(virtual CCAP) system and method for hybrid fiber CATV (HFC) cablenetworks. The system uses a new type of digital optical fiber node(DOFN) configured to receive optical fiber data packets, andreconstitute the optical data packets into RF waveforms suitable forinjection into the system's CATV cable. The system uses the virtual CCAPto essentially replace legacy HFC head ends with a simplified “virtualhead ends”. The invention's virtual CCAP (often spoken of in thealternative as a “virtual head end”) operates using a new type ofvirtual CCAP controller (often abbreviated as “controller) and virtualCCAP software (often abbreviated as “software”) that in turn controlshigh performance edge routers. Much of the intelligence of running theHFC cable system is managed by the controller software, while the edgerouter manages the interface between the CATV portion of the system andoutside networks. The system can handle even legacy CATV RF signals byappropriate conversion operations, while reducing power and space needs,and improving operational flexibility.

The present invention's virtual CCAP system and method is based upon asubstantial amount of recent work by the inventor, much of which wasrecently disclosed in the various priority documents referenced by thisdisclosure (in particular U.S. patent application 61/870,226, U.S. Ser.No. 13/674,936 and U.S. Ser. No. 13/756,302). To thus adequately explainthe present invention, it will be necessary to explain the context inwhich the present form of the invention was derived. Thus a substantialportion of the present disclosure will focus first on a review of theinventor's recent work on systems and methods to provide HFC networkswhere the optical fiber portion of the network transmits information ina pure digital format, while the CATV RF cable portion of the networkmay continue to transmit legacy CATV RF waveforms. Once this portion ofthe invention is disclosed, which in turn is heavily utilized in thisdisclosure's virtual CCAP/virtual head end art, it can in turn be usedas a foundation upon which to better explain the it will be easier toexplain the invention's virtual CCAP/virtual head end art.

Thus the present application, which focuses on concepts to providevirtualized converged cable access platform technology (virtual CCAParchitecture), can be viewed, in part, as a further refinement of theconcepts previously discussed in applicant's U.S. patent applicationSer. No. 13/756,302, the contents of which are directly incorporated inthe present disclosure. Thus in this specification, the teachings ofapplicant's recent U.S. patent application Ser. No. 13/756,302 are firstand reviewed. Following this review, the present further refinements andvariants of the present application, which focus more specifically oncertain virtual CCAP architecture concepts, will then be discussed.

As previously discussed in applicant's previous U.S. Ser. No. 13/756,302disclosure, as user demand for ever increasing amounts of downstream andupstream bandwidth increases, further improvement and advances in HFCtechnology are needed.

The U.S. Ser. No. 13/756,302 and U.S. Ser. No. 13/674,936 art was based,in part, upon the insight that in order to make further advances in HFCtechnology, deviations from both the prior art schemes to allocateupstream and downstream data on the CATV portion of the HFC network, anddeviations from the prior art schemes to allocate upstream anddownstream data on the fiber portion of the HFC system, would be useful.

The optical waveforms presently used on the fiber portion of opticalfiber wavelengths of present HFC systems are often just frequencyshifted versions of the same waveforms used to transmit RF signals onthe CATV cable. Although these direct RF to optical and back to RFwaveform reproduction methods have the advantage of simplicity, due tovarious optical fiber signal propagation effects, such as Ramanscattering, such RF to optical shifted CATV waveforms make inefficientuse of available optical fiber spectrum. This is because due to thesevarious optical fiber effects, the various waveforms become smeared ordistorted, resulting in crosstalk between neighboring optical fiberwavelengths, and the optical versions of the basic RF CATV waveforms arenot at all optimized to cope with these effects.

The U.S. Ser. No. 13/756,302 art and U.S. Ser. No. 13/674,936 art wasalso based, in part, on the insight that by shifting to alternativetypes of waveforms, such as the waveforms used to transmit GigabyteEthernet (GigE) signals (which often use more distortion resistantwaveforms such as binary phase shift keyed (BPSK) or quadraphase-shiftkeying (QPSK) modulation), a much higher amount of data may be sent overthe optical fiber. The rate of data transmission per wavelength can bemuch higher, and different wavelengths may be spaced much closertogether. Other benefits, such as lower noise level, and less powerutilization, may also be realized.

The burdens of shifting from legacy HFC systems, which operate byessentially sending the optical counterparts of standard CATV RFwaveforms, such as optical versions of QAM waveforms, over opticalfiber, to a more advanced system that operates with alternative types ofwaveforms, should be appreciated. Over the years, there has been anexpenditure of tens of billions of dollars or more in legacy HFC systeminfrastructure, along with a huge investment in various software systemsto manage this legacy infrastructure. It is simply not practical toscrap this massive investment overnight.

The U.S. Ser. No. 13/756,302 and U.S. Ser. No. 13/674,936 art was alsobased, in part, on the insight that to minimize the cost oftransitioning to a next-generation digital optical fiber based HFCsystem, those solutions that at least initially preserve large portionsof legacy HFC systems, while also providing the benefits of digitaloptical fiber transmission, will often be preferable. In particular,“plug-in” head-end solutions, which enable legacy HFC head end systemsto continue to operate by generating various RF waveforms at the headend, but which then efficiently demodulate or digitize these RFwaveforms for optical fiber transmission have benefits in this regard.These “plug-in” head end solutions will work in conjunction with“plug-in” optical fiber node solutions that can then also efficientlyremodulate, or digital to analog convert, the digital optical fiber databack into various RF waveforms suitable for injection into neighborhoodCATV cable. Such “plug-in” solutions can, for example, minimize theburden of writing new management software because the process ofdemodulating or digitizing RF waveforms, although of course requiringsome hardware for this purpose, is from a software perspectiverelatively simple. Even the process of compressing and decompressingthis data before and after digital optical fiber transmission is alsorelatively simple. Similarly the process of taking the opticallytransmitted demodulated data or digitized data and in turn using it tomodulate various CATV RF transmitters (or digital to analog converters)at the optical fiber node, although again requiring some new opticalfiber node hardware, is also not complex from the software perspective.To the operator of the HFC system, the transition to digital opticalfiber transmission can be, at least at first, almost totallytransparent. The operator can continue to operate the head end usinglegacy software and systems, yet reap the benefits of digital opticalfiber data transmission.

An additional advantage was that once suitable next generation digitalfiber optic nodes (DOFN) are in place, the HFC system operator thengains the freedom to make additional head end improvements. Inparticular, legacy equipment that generates head end RF waveforms cangradually be phased out, and the head end equipment eventually bereplaced with equipment that simply transmits digital data to thevarious CATV digital optical fiber nodes, according to a schedule thatmakes sense to the HFC system operator. The invention thus provides agentle path that allows a legacy HFC system to be upgraded to a moreefficient and more flexible all-digital (at least prior to the actualneighborhood CATV cable, which may still rely on RF waveforms asdesired) system as a gradual series of steps.

According to applicant's more recent insights virtual CCAP architectureconcepts, previously disclosed in U.S. provisional application61/870,226, also used as a priority document for the present disclosure,further improvements are still desirable. In particular, improvedmethods of reducing the space and power requirements for providing headend cable access functionality is desirable. This can be done, in part,by combining edge QAM functions with various cable modem terminationsystem (CTMS) functions, as described herein.

Much of other prior art to increase the data carrying capability of CATVsystems has focused on various iterations of the Data-Over-Cable ServiceInterface Specifications (DOCSIS) standards. Recent developments inthese standards are exemplified by the Data-Over-Cable Service InterfaceSpecifications Converged Cable Access Platform Converged Cable AccessPlatform Architecture Technical Report CM-TR-CCAP-V03-120511, releasedMay 11, 2012, the contents of which are incorporated herein byreference.

Other recent versions of this system are exemplified by theData-Over-Cable Service Interface Specifications Converged Cable AccessPlatform (CCAP™) Operations Support System Interface SpecificationCM-SP-CCAP-OSSI-I05-130808, the contents of which are incorporatedherein by reference.

As previously disclosed in priority application U.S. Ser. No. 13/756,302and U.S. Ser. No. 13/674,936, and as reiterated herein, art wasdisclosed that was relevant to various methods of converting legacy HFCCATV cable systems, which transmit data over the optical fiber portionof the system using the optical counterpart of analog RF waveforms, suchas RF QAM waveforms transduced to corresponding optical QAM waveforms,to improved HFC CATV systems that transmit data over the optical fiberusing optical fiber optimized protocols, such as Ethernet frames andother optical fiber optimized digital transport protocols. Thus mostaspects of the legacy HFC CATV system may be retained, however at theCATV head end, the optical fiber transmitter system may be replaced byan improved system that extracts the underlying symbols from legacywaveforms, packages these symbols into optical fiber optimized packets,and transmits downstream. The legacy optical fiber nodes may be replacedwith improved nodes capable of receiving the packets and remodulatingthe symbols into RF waveforms suitable for injection into the system'sCATV cable.

The present application and invention is based, in part, on the furtherinsight that once only digital signals are transmitted over the opticalfiber, then this creates an opportunity to further streamline andimprove the HFC cable head end. In particular, although recent work inthis field has taught various attempts to provide Converged Cable AccessPlatforms (CCAP), once only digital signals are being transmitted overthe optical fiber, CCAP systems can be simplified and virtualized to amuch greater extent than was previously contemplated or previouslybelieved to be possible.

In particular, the invention is based, in part, on the concept thatfurther virtualization of the Converged Cable Access Platform (CCAP) asa type of improved cable head end, combined with use of digital opticalfiber nodes (DOFN) previously taught in applicant's recent parentapplication Ser. Nos. 13/756,302 and 13/674,936 (and also discussedherein), is both possible and desirable. Such an improved virtual cableconverged access platforms enable a comparatively simple and low cost toimplement, yet extremely capable and high capacity improved HFC CATVsystem with a new type of virtual head end.

The invention is also based, in part, on the insight that it would beuseful to map DOCSIS functionality onto edge router functionality. Theinvention in particular explores how legacy head end HFC cable systemscan be almost entirely replaced with the invention's controllers, edgerouters, and invention's digital optical fiber nodes, also called“Gainspeed Ethernodes”. Of course new (non-legacy) HFC cable systems canalso be constructed according to this art as well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an overall view of the various frequencies and datachannels that are presently allocated for a typical CATV cable carryinglegacy analog television FDM channels, QAM digital television channels,and various types of DOCSIS data.

FIG. 2 shows an overall view of the various wavelengths allocated forprior art optical fiber wavelength division multiplexing schemes (150)and dense wavelength division multiplexing (DWDM) schemes (160).Although the present invention may use DWDM methods, it does not requirethem, and to some extent reduces the need for DWDM methods because itcan fit more types of digital data onto a single wavelength using, forexample, GigE optical data packets (170).

FIG. 3 shows a simplified version of how prior art HFC systems transmitdata from the cable head to different optical fiber nodes servingdifferent neighborhoods.

FIG. 4A shows an overview of how certain aspects of the invention may beused to upgrade a portion of a legacy analog optical fiber based HFCCATV cable system by replacing the analog modulators and demodulators oneither end of the system with digital demodulators and remodulators. Aswill be discussed, the legacy head end may also be upgraded as well.

FIG. 4B shows a more detailed overview of how certain aspects of theinvention may be used to upgrade a portion of a legacy analog opticalfiber based HFC CATV cable system that is was transmitting a mixture ofconsisting of a plurality of video QAM channels and IP data, such asDOCSIS IP data. Here the legacy QAM channels may be demodulated intotheir underlying QAM constellation symbols. This QAM symbol data, alongwith the legacy IP data, can be encapsulated into various digitaloptical data packets, and transmitted over the optical fiber in thismore efficient form. At the optical fiber node, the data packets can beparsed, and the QAM channels regenerated by remodulated by using the QAMconstellation symbols to drive various optical fiber node QAM RFtransmitters. The data may also be suitably compressed and decompressed,as desired, to further improve the efficiency and speed of datatransmission. The IP data can also be extracted from the optical datapackets, and used to feed an optical fiber node based CMTS system.Upgrading the head end will be discussed in subsequent figures.

FIG. 4C shows still more detailed of how certain aspects of theinvention may be used to upgrade at least a portion of a legacy analogoptical fiber based HFC CATV cable system that is was transmitting amixture of consisting of a plurality of legacy video QAM channels, otheranalog RF channels such legacy NTSC video channels, and legacy IP data,such as DOCSIS IP data. Here the legacy QAM channels may be demodulatedinto their underlying QAM constellation symbols. The other RF videochannels may be handled by digitization and optional compression, asdesired. This QAM symbol data, digitized RF channel data and the legacyIP data, can be encapsulated into various digital optical data packets,and transmitted over the optical fiber. At the DOFN optical fiber node,the data packets can be parsed, and the QAM channels regenerated orremodulated by using the QAM constellation symbols to drive variousoptical fiber node QAM RF transmitters, and the digitized analog RFchannels optionally decompressed and fed into an electrical systemcomprising a digital to analog converter to regenerate the analog RFchannels. The three types of RF waveforms can then be combined andinjected into the neighborhood CATV cable system as before. Again,upgrading the head end will be discussed in subsequent figures

FIG. 4D contrasts the difference in downstream data transmission betweena prior art HFC system that operates using a 1310 nm optical fiberinfrared signal analog according to typical CATV waveforms (e.g. manyQAM waveforms), and the invention's improved digital transmissionmethods. In contrast to prior art, because the invention can transmitall CATV data in digital form using various data packets, the highereffective data rate and superior addressing capability of IP datapackets allows more different types of data to be sent on the samewavelength. The invention preserves backward compatibility by providingvarious converters to convert back and forth between legacy waveformsand IP data packets.

FIG. 5 shows an overview of the invention in operation in downstreammode, showing how the improved “smart” D-CMRTS, also called DOFN, fibernodes can transport a higher effective amount of customized datadownstream for users.

FIG. 6 shows how the invention may also reparation the CATVupstream/downstream frequency split from the standard (US) 5-42 MHzupstream frequency range, into an alternate and often broader upstreamfrequency range. This helps the system transmit a far greater amount ofupstream data from local neighborhoods to the cable head.

FIG. 7 shows a more detailed view showing one embodiment of how theD-CMRTS or DOFN fiber nodes may operate.

FIG. 8 shows additional details of how the CMRTS portion of the D-CMRTSor DOFN fiber node may operate. The CMRTS portion provides much of thehigher functionality of the system.

FIG. 9 shows more details of how the virtual shelf manager and theconfiguration database may control the functionality of most or all ofthe various D-CMRTS of DOFN fiber nodes, and optionally other activenodes and switches in the HFC network system. This virtual shelf managerand configuration database may exist, at least in software, in twopossible forms. One form may be used to manage a legacy head end (202),while, as will be discussed, another form may be used to manage avirtual CCAP/virtual head end, usually in the form of virtual CCAPcontroller software.

FIG. 10 shows a residential gateway (1100) that can also convert betweena CATV cable system with an extended frequency allocated for upstreamdata (e.g. 5-547 MHz or alternative upstream range of frequencies), andresidential equipment designed for the standard 5-42 MHz range ofupstream frequencies.

FIG. 11 shows one embodiment of the virtual converged cable accessplatform (e.g. virtual CCAP, virtual cable head).

FIG. 11A is based on FIG. 4C previously described herein, and shows howthe various functions of the cable head end are now handled by thepresent invention's virtual converged cable access platform (show inFIG. 11, and also in the following figures). Here the previouslydiscussed Digital Optical Fiber Nodes (now referred to as the GainspeedEtherNodes) continue to handle the interface between the cable RFsignals, and the optical fiber data.

FIG. 12 shows a detail showing the system's high-level operationalworkflow.

FIG. 13 shows additional details of the system's high-level operationalworkflow.

FIG. 14 shows some details of the system's Business Services over DOCSIS(BSoD) workflow

FIG. 15 shows an example of the various protocol operations according tothe invention's virtual converged cable access platform.

DETAILED DESCRIPTION OF THE INVENTION

Nomenclature: In this specification, the term “legacy signals” whenpertaining to RF waveforms, will often be used to describe various olderstandard CATV RF signals such as NTSC (television) signals, FM radiosignals, set top box signals and the like. It should be understood,however, that the invention's methods will in fact operate with any typeof RF signal. Thus the term legacy signals, although intended to improvereadability by reminding the reader that the invention's methods areparticularly useful for coping with various CATV legacy RF waveforms, isnot otherwise intended to be limiting.

Legacy signals, when pertaining to optical fiber transmission methods,will generally refer to prior art methods which simply transformed theRF waveforms, such as QAM RF waveforms, into optical waveforms whileretaining the essential characteristics (e.g. shape) of the RFwaveforms.

Continued Discussion:

Although this particular specification is more focused on the head endof the HFC system, note this is head end improvement is in turn based ona number of previously discussed HFC system improvements. For the sakeof completeness, and to provide an overall picture of how many of theseimprovements can be combined to incrementally produce a very advancedHFC system with both improved cable heads and improved optical fibernodes, these various CATV cable system upgrades will also be described.

Prior art CATV systems use the radio-frequency (RF) CATV cable spectruminefficiently. Much of the available 5 MHz to approximately 1 GHz CATVfrequency is presently filled up with QAM channels that, most of thetime, are carrying downstream data that is not actually being used (atthat time) by the various households that are connected to the cable.Another problem with prior art approaches is that only a tiny region ofCATV spectrum (usually 5-42 MHz), is allocated for upstream data. Thisrelatively narrow region of frequencies must carry the upstream data forthe entire CATV neighborhood. This results in great limitations on thebandwidth or amount of data that can be uploaded from the varioushouseholds. Thus typical CATV systems are asymmetric, with thedownstream data rates being much higher than the upstream data rates.

Thus one aspect of the present disclosure teaches new HFC systems andmethods to carry much higher amounts of upstream and downstream data. Onthe fiber portion of the HFC system, the disclosure teaches use ofnon-CATV compatible waveforms (e.g. GigE rather than QAM waveforms)which can carry much higher amounts of data over long distances. On thecable portion of the HFC system, art relevant to improved systems andmethods that utilize the limited 5 MHz to 1-GHz bandwidth of CATV cablemore efficiently is also taught.

The improved head end concepts of the present invention rely, in part,on the use of intelligent optical fiber nodes, such as those previouslytaught in the various priority documents.

In some embodiments, the invention may be a system or a method based ondigital optical fiber nodes operating in a Hybrid-Fiber CATV-Cable (HFC)network. Such systems generally comprise a cable head end (here animproved cable head end is also taught), which is often in IPcommunication with an IP backbone such as the Internet or other highspeed digital network. These HFC networks also generally also compriseone or more optical fibers in communication with the head end, as wellas at least one and often many digital optical fiber nodes (DOFN).

These digital optical fiber nodes have some elements in common with theCable Modem Remote Termination Systems (CMRTS) and Digital Cable ModemRemote Termination systems (D-CMRTS) previously described by inventor inapplications such as Ser. No. 13/674,936 the contents of which areincorporated herein by reference. As a result, these digital opticalfiber nodes (DOFN) will frequently be discussed in the alternative inthis disclosure as D-CMRTS units, or as Gainspeed EtherNodes.

To form an HFC system (using either a legacy head end or the presentlydisclosed improved head end), these various DOFN or D-CMRTS units willbe connected to (i.e. in RF communication with) various CATV cables(e.g. coax cable, capable of RF transmissions), and at least one CATVcable device which will be various cable modems, set top boxes, digitaltelevisions, computers, and the like.

Although, as discussed in the earlier disclosures, the inventor'searlier D-CMRTS/DOFN units were designed from the beginning with a highcapability to provide additional data handing capability to CATV systems(e.g. above and beyond the present DOCSIS 3.0 standard), one challengingproblem is how to provide even more functionality while still providingthe ability to gracefully operate in an environment with varying amountsof legacy equipment. As will be discussed, the DOFN can operate witheither legacy head ends, or with the improved virtual CCAP head endsdisclosed herein.

A unique aspect of the present disclosure is that the improved DOFN orD-CMRTS units disclosed herein, while providing advanced functionality,and often totally abandoning use of optical versions of the standardQAM, NTSC, FM waveforms on optical fiber, can still be highly capable ofoperating with legacy equipment.

Here, systems are disclosed that are designed with a high capability tooperate in the digital optical fiber domain (e.g. using optical fiberdigital transport protocols such as GigE) while still providing CATV RFsignals carrying various types of legacy analog CATV RF waveforms, suchas analog NTSC television channels, FM audio channels, QPSK channels,QAM channels and the like. The present methods have the additionaladvantage that because digital data transport protocols can easily carrydata packets to and from many alternative addresses, the invention'smethods can operate without requiring the use of, for example, largenumbers of alternative optical fiber wavelengths. By contrast, underprior art methods, use of large numbers of alternative optical fiberwavelengths was required in order to accommodate the many differenttypes of analog legacy CATV waveforms that can originate from manydifferent types of legacy optical fiber nodes.

According to this disclosure, such improvements can be made by, forexample, converting legacy CATV analog waveforms to a digital form byhigh speed analog to digital converters and or QAM waveform demodulationinto the underlying QAM symbols. This approach has the advantage thatthese waveforms can then be transformed to digital data packets (IP datapackets) without the system otherwise needing to understand what theunderlying data content of the waveforms is.

Such QAM symbol methods were previously disclosed by inventor ininventor's copending U.S. patent application Ser. No. 13/478,461“EFFICIENT BANDWIDTH UTILIZATION METHODS FOR CATV DOCSIS CHANNELS ANDOTHER APPLICATIONS”, the contents of which are incorporated herein byreference.

The digitized waveform data can then be transported as IP packets overthe HFC optical fibers using digital optical fiber data transmissionformat such as GigE.

More specifically, CATV legacy downstream RF waveforms of any type (e.g.NTSC, FM, QPSK) and/or more standard CATV downstream RF waveforms suchas various QAM waveforms can be digitized by using a high speed analogto digital converter or other method to sample and digitize these legacydownstream RF waveforms, thus producing digital samples of the legacydownstream RF waveforms. This digital data which can then be convertedto IP packets and sent over the optical fiber. Alternatively, and moreefficiently in the case where more standard RF QAM waveforms are beingtransmitted downstream, these RF QAM waveforms, which are complexwaveforms constructed using various underlying QAM symbols, may bedemodulated and the underlying QAM symbols determined. These demodulatedQAM symbols can then also be converted to various data packets andoptically transmitted downstream over the HFC optical fiber or fibers.

Once in the form of IP data packets, low cost equipment such asinexpensive switches can then be used to easily sort and transport theseIP data packets to and from various devices. Indeed, as will bediscussed, entire legacy head ends can be replaced with improved headends based upon relatively inexpensive high capacity switches such asedge routers, and appropriate control software and systems.

To reconstruct these various legacy CATV RF waveforms, at the digitaloptical fiber node(s) or D-CMRTS/DOFN unit(s), various RF digitalreconstitution devices may be configured to accept the digital samplesof downstream RF waveforms (which were digitally transmitted downstreamover the optical fiber), and reconstitute these digital waveform samplesinto one or more downstream digitally reconstituted RF waveformschannels that essentially reproduce the original RF waveforms.

Alternatively or additionally, at the digital optical fiber node(s) orD-CMRTS/DOFN unit(s) there can also be one or more remodulator devicesconfigured to accept the downstream digital QAM symbols that weretransmitted over the optical fiber, and remodulate these QAM symbolsinto one or more downstream QAM symbol, again producing remodulated RFQAM waveforms and channels that essentially reproduce the original RFQAM channels.

To provide still higher levels of service (e.g. to provide higher CATVdata carrying capability, and provide functionality beyond the presentDOCSIS 3.0 standard), the digital optical fiber nodes or D-CMRTS/DOFNunits will often also contain one or more IP to QAM conversion devicessuch as QAM modulators. These QAM modulators may be configured to acceptdownstream digital IP data packets transmitted over the optical fiber,and to modulate these digital IP data packets into one or moredownstream IP based RF QAM channels. These can be broadcast QAMchannels, narrowcast QAM channels, on-demand QAM channels, and so on.

Often, according to applicant's art, the digital optical fiber nodes orD-CMRTS/DOFN units will employ two or more of the above options, andwill thus use a RF combiner device configured to combine any of thesedigitally reconstituted RF channels, QAM symbol remodulated RF QAMchannels and these IP based RF QAM channels, and then transmit thesevarious RF channels downstream over the CATV cable to the various CATVcable devices.

In one embodiment, applicant further teaches a method of convertinglegacy HFC CATV cable systems, which transmit data over the opticalfiber portion of the system using the optical counterpart of analog RFwaveforms, such as RF QAM waveforms transduced to corresponding opticalQAM waveforms, to improved HFC CATV systems that transmit data over theoptical fiber using optical fiber optimized protocols, such as Ethernetframes and other optical fiber optimized digital transport protocols.According to this embodiment, many aspects of the legacy HFC CATV systemmay be retained.

Here, at the CATV head end, if the user wishes to retain the legacy headend, the optical fiber transmitter system may be replaced by an improvedsystem that extracts the underlying symbols from legacy waveforms,packages these symbols into optical fiber optimized packets, andtransmits downstream. The legacy optical fiber nodes are replaced withimproved optical fiber nodes capable of receiving the packets andremodulating the symbols into RF waveforms suitable for injection intothe system's CATV cable. Alternative methods based upon using animproved virtual CCAP/virtual head end will be discussed shortly.

Optical Fiber Data Transmission Methods:

As previously discussed, prior art schemes of transmitting HFC data inthe form of one or more CATV analog modulated wavelengths of light,along optical fiber, tended to be inefficient. That is, the prior artmethods limited the amount of data that could be sent. This is becausethe analog waveforms used to transmit RF signals on CATV cable workinefficiently when transposed to optical wavelengths. Due to variouseffects including Raman scattering, and other nonlinear optical fibereffects, when too many analog modulated light wavelengths are placedonto an optical fiber too close together (in terms of wavelengthdifferences), cross-talk between the different wavelengths tends todegrade the complex CATV RF analog signals (usually composed of many QAMmodulated waveforms) to the point where crosstalk may render the signalsuseless.

As a result, to prevent the CATV modulated analog signal fromdegradation when carried over optical fiber, the wavelengths must berather widely spread out. Thus due to cross talk effects, an opticalfiber may only be capable of transmitting a few (e.g. 8) inefficientlymodulated CATV signals, each transmitting about 6 Gigabits of data persecond.

By contrast, if more efficiently digitally modulated signals (e.g. GigEdata formats) were used, the same stretch of optical fiber might becapable of transmitting many more wavelengths (e.g. 80) of signals, andeach wavelength in turn may transmit far more data, such as between10-100 Gigabits of data per second.

Application 12/692,582, now (U.S. Pat. No. 8,311,412) taught theadvantages of producing a new type of optical fiber node, there called aCable Modem Remote Termination System (CMRTS) device, which essentiallypushed much of the functionality (such as generating QAM signals) of theprior art Cable Modem Termination Systems (CMTS) from the central cablehead down to many distributed optical fiber nodes servicing neighborhoodCATV cables. Thus according to application 12/692,582, non-CATVcompliant signals may be sent to and from the central cable head tovarious remote CMRTS optical fiber nodes by optical fibers carryinglight modulated by more efficient digital Ethernet protocols (e.g. GigEsignals). The CMRTS optical fiber nodes then converts these non-CATVcompliant signals into CATV compliant RF signals, such as a plurality ofdifferent RF QAM modulated signals, and/or other types of signals.

Parent and copending application U.S. Ser. No. 13/674,936, which was aCIP of Ser. No. 12/692,582, further built upon this concept, and furthertaught the advantages that can be obtained by reducing or droppingadditional backward compatibility requirements, such as the requirementthat legacy RF waveforms (e.g. QAM waveforms) be transmitted along theHFC optical fiber(s) while preserving the essential waveformcharacteristics (e.g. requiring that the optical QAM waveforms be thesame as the RF QAM waveforms).

Other departures from pure backward compatibility may also be reduced.For example, according to the invention, the prior art CATV upstreamrequirements that upstream data must be carried as a number of 2 MHzwide QAM channels in the 5-42 MHz region, may be dropped in favor ofalternate upstream schemes that provide for greater amounts of upstreamdata to be transmitted. That is the 5-42 MHz region may be extended intothe higher frequency ranges—for example extended to the 5-547 MHzregion, which will allow for a higher rate of upstream data to betransmitted, but of course will cut into the rate of transmission ofdownstream data.

In some aspects, the present invention can be viewed as dropping stillone more requirement for head end backward compatibility, in favor ofthe present virtual CCAP/virtual head end concepts.

However even if the upstream bandwidth problem is solved at the CATVcable side of the HFC system, the optical fiber itself, if usedaccording to prior art schemes (e.g. shove the analog signal over theoptical fiber in an essentially unchanged form) will now be ratelimiting. That is, if a large number of different neighborhoods, eachwith their own stretch of CATV cable, are now enabled to starttransmitting much more upstream data, unless the method of sending dataover the fiber portion of the HFC network is changed, there will soon bea bottleneck at the fiber stage. This is because the prior art HFCmethods of handing upstream data would, in general, simply convert theanalog RF modulated CATV upstream waveforms into equivalently modulatedoptical fiber infrared light waveforms, and then transmit this data backover the optical fiber. Although such conversion processes can be easilydone with inexpensive converters, this scheme has the drawback, aspreviously discussed, that they are not optimized for optical fiber.Consider the problem of pooling upstream data from multipleneighborhoods. Although the data CATV RF data from each neighborhoodmight be converted to a slightly different infrared frequency, put onoptical fibers, the fibers combined and a composite multiple wavelengthsignals sent upstream, the inefficient CATV RF modulation schemes meanthat each wavelength will carry only a relatively small amount of data.Further, due to crosstalk effects, the number of different neighborhoodsworth of data that can be pooled is also limited. So due to prior-artinefficiencies, the potentially very large ability of the optical fiberto carry upstream data rapidly becomes limiting.

However, again by reducing the requirements that the HFC system be fullybackward compatible in terms of inefficiently carrying legacy analog RFwaveforms over optical fiber; the much higher amount of upstreambandwidth that would be generated under the invention can now be handledby repackaging the upstream data into more efficient modulation formats,such as the digital (GigE) modulation format, before transmitting thedata on the optical fiber. Thus, according to the present invention, asmaller number of higher data density and more efficiently modulatedoptical fiber optimized signals, such as GigE data packets may now sent.This overcomes the inefficiencies of prior-art optical fiber modulationschemes, and helps remove the optical fiber upstream transmissionbottleneck.

As per inventor's previously disclosed U.S. patent application Ser. Nos.12/692,582 and 13/674,936, the present disclosure relies, in part, upona radically different CMTS design in which the QAM modulators in theCMTS PHY section (used to ultimately provide the waveforms used to sendRF data signals to a given individual cable) are often not located atthe central cable head, but rather are divided and pushed out to thedistant optical fiber nodes of the HFC network. That is, in contrast toprior art designs, were the QAM modulators were are located in the PHYunits of main (centralized, e.g.—cable head) CMTS line cards on thecentral CMTS units; in the present invention, some or all of the QAMmodulators are located in the PHY sections of remote or distributedCMRTS optical fiber nodes.

Inventor's recently disclosed parent U.S. application Ser. No.13/674,936 taught that, as a less favored embodiment, and when greatercompatibility with legacy equipment is desired, at least some of the QAMmodulators or other RF signal generators such as NTSC television, FMradio, set top box QPSK signals and the like can still remain at thehead end.

By contrast, the present specification now requires that all legacy RFwaveforms previously output by the legacy head end equipment, and nowoutput by the invention's improved virtual CCAP head end, must bedigitized before optical transmission. This digitization can be done byvarious means, including high frequency analog to digital sampling, orby for example demodulating various QAM or OFDM waveforms, determiningthe underlying QAM or OFDM symbols used to generate the QAM or OFDMwaveforms, and digitally sending the results. At the optical fiber node,these RF waveforms can then be regenerated, for example by digital toanalog conversion and RF modulation, or using the digitally sent QAM orOFDM symbols to control one or more RF QAM or OFDM modulators.

Thus, according to the present invention, essentially all data will betransmitted downstream and upstream over the optical fiber to thevarious DOFN optical fiber nodes in a digital format. This digitalformat may be in the form of standard IP packet type digital data.Upstream data will also be transmitted in a digital form as well. TheDOFN optical fiber nodes can examine the data packets, determine whichpackets correspond to what signals, and for example then use theappropriate data packets to drive various optical fiber located RF QAMmodulators (e.g. for broadcast QAM signals, narrowcast QAM signals,DOCSIS QAM signals, etc.) as desired.

When the present disclosure merely speaks to more incremental upgradesin the head end of the HFC system, which can be a useful intermediatestep to understanding how the invention's virtual CCAP methods operate,the higher capacity cable modem termination system (CMTS) at the headend will often be referred to as D-CMTS units, where the D again is usedto symbolize the digital encoding capability of the D-CMTS units. Theoutputs from these units are generally used to drive one or morehead-end optical fiber lasers (e.g. optical transmitters). These opticalfiber laser transmitters, and their associated electronic equipment, areoften referred to as legacy optical fiber transmitter systems.

As per the CMRTS units that were previously disclosed in Ser. No.12/692,582, the D-CMRTS/DOFN units disclosed herein will often also belocated at the final network fiber nodes (FN) between the fiber portionsof the HFC system, and the cable portions of the HFC system.

In the CMTS systems previously disclosed in U.S. application Ser. No.12/692,582, some QAM modulators were located in the centralized CMTS PHYsections at an upgraded legacy version of the cable head, while some QAMmodulators were located at the remote CMRTS units. The upgraded legacycable head CMTS QAM modulators were used for sending data, such as astandardized package of cable TV channels and perhaps a basic level ofDOCSIS service, which might be generally requested by manyneighborhoods; over optical fiber using RF CATV (e.g. QAM) modulatedinfrared light signals. This helped maintain backward compatibility withprior art HFC systems. The present application abandons this, andinstead sends out only digital data from the virtual CCAP head end.

In this present disclosure, and as previously anticipated by applicant'spriority documents, U.S. Ser. No. 13/674,936 and U.S. Ser. No.13/756,302, in order to focus on aspects of the invention that canprovide higher amounts of upstream and downstream data to subscribers,this type of backward compatibility now abandoned. In the presentembodiment, all data traveling over the optical fiber will be digitallyencoded according to optical fiber optimized formats, rather than simplyoptical versions of legacy RF waveforms.

When used in a less preferred embodiment with legacy head ends, or evenas needed with the invention's all digital virtual CCAP head end, tomaintain backward compatibility, the various legacy head end waveforms,such as QAM waveforms, NTSC television waveforms, QPSK waveforms and thelike (during transmission over optical fiber both downstream from thehead end to the optical fiber nodes, and upstream from the optical fibernodes to the head end) can be digitized prior to transmission by variousmethods, and then reconstituted after optical fiber transmission asneeded. As previously discussed, these digitization methods can rangefrom brute force (i.e. simple high speed analog to digital sampling ataround the Nyquist frequency (e.g. 2× the highest frequency of theunderlying waveform), as well as more sophisticated methods such asdemodulating the various QAM or OFDM waveforms to extract the underlyingQAM or OFDM symbols used to produce the RF waveforms in the first place.

Often the brute force, high frequency analog to digital sampling methodsmay be more suitable for legacy NTSC, FM, or QPSK waveforms (channels).By contrast, QAM or OFDM demodulation methods may be more suitable forQAM channels transmitting various SD or HD digital television, DOCSISQAM or OFDM channels, and the like.

Thus the preferred embodiment of the present invention may have no QAMmodulators at the virtual CCAP cable head whatsoever, and send purenon-CATV compatible waveforms (e.g. digital IP data packets) through theoptical fibers. These systems may rely on the remote D-CMRTS/DOFN unitsto generate all of the downstream QAM signals in the system.

Thus in one embodiment, the invention may be a method for enhancing thedata carrying capacity of a hybrid fiber cable (HFC) network with eithera legacy cable head or an improved cable head, an optical fiber network,a plurality of optical fiber nodes, a plurality of individual CATVcables connected to the plurality of optical fiber nodes (D-CMRTS/DOFNunits), and a plurality of individual cable modems, each with differingdata requirements, connected to each of the individual CATV cables.

This method may work by using at least one optical fiber, operating atone or more wavelengths, to transport a first set of downstream datafrom the either legacy or improved cable head to the optical fibernodes. This first set of downstream data will generally be transmittedin a digital format that is not capable of being directly injected intoindividual CATV cables by simple optical to RF converters.

Here, generally so much data may be transmitted that if all of the firstset of downstream data was converted into RF QAM waveforms, thebandwidth of this data would exceed the available bandwidth of any ofthe individual CATV cables in the system. To avoid this problem,generally only a selected portion of this first set of downstream datawill be converted into downstream RF QAM waveforms at these opticalfiber nodes.

What portions of the optical fiber downstream data are selected for anygiven CATV cable neighborhood (with its own optical fiber node and CATVcable) may differ. At the optical fiber nodes, data packets will beselected, and these selected data packets will be converted intodownstream RF QAM waveforms that in turn will be injected into theindividual CATV cables.

Here, the main constraint is that for each individual CATV cable thedownstream RF QAM waveforms should be selected so that the sum total ofthe selected downstream RF QAM waveforms does not exceed the availablebandwidth of the individual CATV cables.

In a preferred embodiment, the invention's D-CMRTS/DOFN units will oftenbe designed to be highly software configurable, so that the ability ofthe D-CMRTS/DOFN units to operate their remote or distributed QAMmodulators to send downstream data, as well as the ability of theD-CMRTS/DOFN units to operate various RF packet processors that receivemultiple RF bursts of modulated upstream data from various cable modems,demodulate the bursts, digitize and reassemble this upstream data intopackets, and retransmit this data back upstream, can be reconfigured byremote software. Such methods can greatly simplify the management andconfiguration of the distributed D-CMRTS/DOFN network. As will bediscussed, this management and configuration process will often bemanaged by the virtual CCAP controller and software (1102).

As one simplified example, in order to supply a standardized set of TVchannels and other services to three cables in three neighborhoods,legacy head end equipment may have QAM modulators in their PHY units(See FIG. 7, 614) set to drive an optical fiber with multiple QAMsignals at optical wavelengths. By contrast, as will be discussed, theinvention's improved virtual head end (virtual CCAP head end) willgenerally entirely lack any QAM modulators, and will generally notoperate in this mode. However FIG. 7 is still useful because theinvention's improved virtual head end has to in essence cope with thelack of head end QAM modulators by instead sending out digitized QAMsymbol data packets instead.

To convert to a legacy head end to digital optical fiber transmission,while maintaining high levels of backward compatibility, as an initialfirst step (later to be abandoned in the virtual CCAP approach), thelegacy head end may have digital converter units (399) (occasionallyreferred to in the alternative as a digital optical fiber transmittersystem), that can intercept output from the legacy head end QAM, FM,QPSK modulators and other RF modulators (614), and digitize this outputby relatively unintelligent methods (high speed analog to digitalconverters, QAM or OFDM waveform demodulation into QAM or OFDM symbols).The digital output from these converters can then be packaged intoappropriate digital data packets, such as GigE data packets, andtransmitted along optical fiber (218) along with other digital traffic(e.g. from GigE PHY modulators 620) to the optical fiber nodes.

Jumping momentarily to FIG. 11, the invention's virtual CCAP approachgenerally assumes that the virtual head end is being fed previouslydigitally converted signals from the various operator servers (1100),although if this is not available, a digital converter unit (300,304)can also be placed in between the operator server (1100) and the virtualhead end (1120) as needed.

In a process where a legacy HFC system is being gradually converted overto the invention's improved system, in some neighborhoods, simple “dumb”converters and “dumb” optical fiber nodes can take this digital datafrom the legacy head end equipment (614), and convert it back to legacyQAM, FM and QPSK signals by various simple methods such as digital toanalog conversion (600), QAM remodulation using the QAM symbols (603),and the like. These “dumb” converters and optical fiber nodes can theninject these reconstituted RF signals into those neighborhood CATVcables (226) that are equipped with “dumb” converters and optical fibernodes.

In the preferred embodiment, as previously discussed, the cable head endmay have no QAM modulators (or other modulators such as FM and QPSKmodulators in their CATV PHY units 614), and all signals going out tothe various D-CMTRS/DOFN optical fiber nodes along the fiber portion ofthe network (218) may be digitally modulated in GigE or other format.

Some of the examples in this specification, such as FIG. 7, show a mixedmode of operation, where a slightly upgraded legacy head end is beingused, and some legacy “dumb” converters and optical fiber nodes in someneighborhoods work in conjunction with more advanced D-CMRTS/DOFNoptical fiber nodes in other neighborhoods. Other examples show a pureGigE mode where backward compatibility with dumb optical fiber nodes isno longer required.

Since the D-CMRTS/DOFN units will often use optical fibers and variousDigital Ethernet (GigE) protocols as their primary means ofcommunication, this GigE fiber data will require conversion,reformatting, and QAM modulation by the components (e.g. 600, 603) inthe remote D-CMRTS units (304). The QAM modulators in the D-CMRTS unitswill then provide a radiofrequency (RF) QAM signal that can be injectedinto the cable, and recognized by cable modems attached to the variouscables.

As previously discussed, one of the biggest advantages of generatingsome or all of the CATV RF data at the local D-CMRTS/DOFN optical fibernode is that vast amounts of data can be carried by the optical fiberusing modulation schemes, such as the various digital GigE datatransmission schemes, that may be optimized for the signal transmissioncharacteristics of the optical fiber media. That is, by eliminating theneed for direct and simple conversion to and from the signal waveforms(often QAM waveforms) used to send RF data on CATV cables, the opticalfiber signals can both carry more data per wavelength, and also allowfor a greater number of signals at nearby optical fiber wavelengths tobe sent with minimal interference.

The present disclosure also relies, in part, upon the observation thatat the present level of rather coarse granularity (where multipleneighborhoods are served by the same CATV QAM signals) the aggregatedemands for IP-on demand data from multiple cables serving multipleneighborhoods may easily saturate the limited CATV bandwidth. That is,absent some sort of customization, it is not possible to send all datato everybody because it won't fit on the CATV cable. However at a finerlevel of granularity (where each neighborhood might get its owncustomized CATV signal), the IP-on demand data for an individualneighborhood is more likely to fit within the limited bandwidth of eachneighborhood's CATV cable.

The trick is thus to avoid overloading each neighborhood's particularCATV cable bandwidth by picking and choosing the mix of standard QAM andQAM IP/on-demand signals are delivered to each neighborhood.

Software Control Methods:

Although when the DOFN are used with legacy or slightly upgraded legacyhead ends, the DOFN approach allows cable operators to largely preserveuse of legacy HFC control software, to the point where at leastinitially, an upgrade to an all digital optical fiber data transmissionscheme can be largely software transparent to both the cable operator aswell as the various CATV user households as well. However as will bediscussed, the virtual CCAP software needed to implement the presentinvention's improved virtual head ends will generally require a moresubstantial software revision. Nonetheless, much of the basic structureand functionality of the legacy HFC control software will be reflectedin the virtual CCAP software used to run the virtual CCAP controller(FIG. 1102), and thus unless otherwise stated, the upgraded softwarewill generally have a similar type basic functionality, but now portedinto the all-digital edge router control realm.

In particular, however, because the invention also uses all digitaloptical fiber data transmission schemes, for still more advancedfunctionality to be implemented as desired, these more advanced(non-transparent) software control methods will also be described.

Certain aspects of the virtual CCAP control software can be adapted fromthe methods previously discussed in applicant's U.S. application Ser.No. 12/692,582, incorporated herein by reference.

The invention's improved virtual CCAP head end may, for example, managethe available bandwidth on the various cables that serve the variousneighborhoods. When used in a less backward compatible, higherperformance mode, such as a phase 3 upgrade step to be discussed lateron in this specification, the computerized system may vary both the“standard” QAM channels (if any) being transmitted by any givenD-CMRT/DOFN, as well as the user-customized or “premium” IP/on-demandQAM or edge QAM channels being transmitted by the various D-CMRTS/DOFNunits.

To contrast with legacy head ends, in CATV jargon, the various CMTSsystems at a legacy cable head are often referred to as a “shelf” or“CMTS shelf” (500). In the present embodiment, the system has completelydistributed the functionality of the CMTS unit from the cable head toD-CMRTS/DOFN units that are distributed to the far-flung optical fibernodes throughout the entire network.

In some situations, it may be useful from a network managementperspective to continue to communicate with the various networkdistributed D-CMRTS/DOFN units as if they were still a single legacycable head CMTS (500). Thus, in one embodiment, this virtual CCAPsoftware that can be used to manage the network distributed CMTS can beconsidered to be “virtual shelf” hardware and software. This is becausethe virtual CCAP controller (1102) and edge router (1104) may bothmanage the complex configuration issues involved in running adistributed CMTS system, and then shield this complexity from the restof the system when needed.

Thus, in some embodiments, the invention's virtual CCAP software, alsocalled the virtual shelf hardware/software system may, for example, takeas inputs, user demand over multiple neighborhoods for basic TV channelsand basic DOCSIS services, user demand in individual neighborhoods foradvanced or premium on-demand TV or premium DOCSIS IP service (IP-ondemand), and the limited number of total QAM channels that can becarried over cable.

In some embodiments, the invention's virtual CCAP software, used tocontrol controller (1102) may instruct the D-CMRTS/DOFN units toreallocate their neighborhood CATV spectrum or modulation scheme toallow for more upstream data to be transmitted. For example, the D-CMRTSunits may work with various CATV cable connected residential gateways(See FIG. 10) to allocate a greater amount of CATV bandwidth to upstreamdata.

The invention's virtual CCAP software (virtual shelf system) may also,through controller (1102) and edge server (1104) then instruct theremote D-CMRTS/DOFN units on the fiber node serving the targetneighborhood to take the IP/on-demand data, decode and QAM modulate thedata using local CMRTS devices (604), and inject this now RF modulatedQAM data on the cable for that particular neighborhood.

The virtual CCAP control system software (virtual shelf system) can alsoinstruct another remote D-CMRTS/DOFN unit on a different fiber nodeserving a different neighborhood to take the IP/on-demand data for thisneighborhood from the massive amount of downstream GigE data, decode andQAM modulate this data and inject this now RF modulated QAM data on thecable for this neighborhood as well.

Note that by this method, the overall CATV QAM channels may not be thesame for each neighborhood. Rather, at least for the IP/On-demand data,the same QAM channel (frequency) may now carry different data fordifferent neighborhoods.

Using these systems and methods, the effective data carrying capacity ofthe various cables and QAM channels has been increased. Yet, at the sametime, if the virtual CCAP software and controller (1102) (virtual shelf)are properly configured, most of the complexity of this more advancedswitching arrangement can still be selectively hidden from both theupstream (cable head) and downstream (cable modem) systems, thusenabling good backward compatibility with existing HFC equipment andsystems as desired.

Equipment Needed to Demodulate/Digitize Legacy Signals:

In the legacy head end embodiments previously taught by applicant, suchas Ser. No. 13/675,936 and other discussions, incorporated herein byreference, in some embodiments, the system could work essentiallyindependently of the legacy CMTS or D-CMTS units at the cable head, andmerely acted to supplement the functionality of prior art legacyequipment by adding a minimal amount of new equipment at the cable head.Although the present application abandons the concept of legacy headends in favor of the present improved head end approach, it is stilluseful to review how legacy head ends may be used, in order to betterunderstand the basic challenges faced in controlling the presentinvention's improved virtual head ends.

One comparatively simple method to upgrade legacy head ends to provideall digital over optical fiber signals is to use various digitalconverters (399) that convert the legacy QAM, FM, QPSK waveforms fordigital output. Unit (399) in this embodiment should also be consideredto have enough onboard computing functionality to extract this data,subsequently package the data into the appropriate digital optical fiberdata transport format, such as various Ethernet packets, and also toprovide the fiber optic light source (e.g. one or more optical fiberlaser transmitters) to transmit the digital optical fiber signals.

For more advanced functionality (e.g. Phase 3 functionality) otheroptional equipment used to upgrade legacy head ends may consist of amedia Level 2/3 switch (629), a virtual shelf management system (622,630), and appropriate MAC and PHY devices to send and receive data alongoptical fibers.

In some embodiments, in order to facilitate the process of upgrading theDOFN from legacy head ends to the present invention's improved virtualhead end, it may be useful to implement the DOFN using softwareconfigurable components (e.g. using FPGA and DSP components), as per theteaching of parent patent application Ser. No. 13/555,170, the contentsof which are incorporated herein by reference. In these embodiments, theHFC system operator need merely send appropriate configuration softwareover the optical fiber to, for example, a phase 1 DOFN to upgrade itscapability, without the need for sending crews out into the field toperform manual DOFN upgrades.

In applicant's earlier disclosures, applicant taught somewhat upgradedlegacy head ends with an advanced D-CMTS/DOFN (Digital Cable ModemTermination System) head (500) with at least a first packet switch, afirst MAC (Media Access Control), and a first PHY (Physical Layer) thatoptionally may be capable of sending and receiving data from a layer 2-3switch to a first end of a first optical fiber as at least a pluralityof first digitally encoded analog QAM waveforms (first optical signals).

Applicant also taught that in other embodiments, this first PHY (614)and MAC (612) may be omitted, and instead the upgraded legacy D-CMTShead may instead use only a second MAC (618) and a second PHY (620)capable of sending and receiving data from the layer 2-3 switch to theoptical fiber.

According to the present invention, essentially the entire cable head(202) and head end (500) equipment is now replaced with the virtual headend (500).

Note however that even under the present invention, some sort of legacyhead end that sends analog signals can still exist, at least on adifferent optical fiber wavelength. That is, as previously discussed,although in the preferred embodiment, all HFC optical fiber signals willbe sent in a digital format, the system can still operate in a stillhigher backward compatible mode. Here a backward compatible wavelength,such as the standard HFC 1310 nm wavelength, may be reserved for priorart analog modulated optical fiber signals (e.g. QAM waveforms) (whichmay then be digitized for optical fiber transmission by a converterunit). The invention's digital signals will then operate on a differentwavelength and a second head end PHY may send and receive data from theIP backbone using this alternate optical wavelength.

In some embodiments, if any legacy signals continue to exist, it may beconvenient to send both any legacy (digitized analog modulated opticalfiber signals) data and the advanced data using similar digitalprotocols (e.g. various IP digital protocols such as GigE). This becausethen the same switches may be used to handle both the legacy signals andthe advanced functionality signals. This is because when all data flowsusing the same type of digital protocol, as then simple switches can beused to send relevant data packets to the relevant destinations, andhandle these data packets using the appropriate equipment once the datapackets reach their intended destination.

As previously discussed, although in some embodiments, data may be sentand received using as many optical fiber wavelengths as desired, theinvention's digital optical fiber transmission techniques can reduce thenecessity for using multiple optical fiber wavelengths, and in turnreduce costs.

In the case where some legacy HFC backward compatibility (at least at adifferent optical fiber wavelength) is still desired, the D-CMRTS/DOFNfiber node(s) may optionally incorporate one or more external “dumb”digital optical to RF (radio frequency) conversion devices (see FIG. 6,401) that directly any and all signals sent on the legacy optical fiberwavelength. These are typically designated as O-D/A-E or A-E/O-D (i.e.optical-digital to analog electronic, or analog electronic to opticaldigital) converters, depending upon the direction of the electrical RFto digital fiber optic conversion. Thus in some embodiments, at least asa backup, this functionality may be incorporated into the D-CMRTS/DOFNnodes as well (e.g. 600, 601, 603, and 605).

In alternate and often more expensive (but higher performance)embodiments where the D-CMRTS/DOFN (300), (304) unit is designed tooperate at a plurality of different optical wavelengths, the units mayincorporate one or more wavelength splitting devices, such as Bragfilters, prisms, gratings, and the like as part of the unit's internalswitch (560), to separate and combine the various optical fiberwavelengths as desired. In some embodiments, these wavelength splittersmay be tunable wavelengths splitters that may operate under softwarecontrol. Although within the scope of the invention, such embodimentstend to be somewhat more expensive due to the costs of the extraequipment. Thus such multiple wavelength embodiments will typically beused more in very high (e.g. demanding) data transport situations.

The D-CMRTS/DOFN may have at least one (and often a plurality of, e.g.as many as 160 or more) CATV RF signal generators, such as QAM or OFDMmodulator devices. These devices will be capable of detecting andencoding selected portions of the digitally encoded optical fiber data(such as the underlying QAM or OFDM symbol data) into various types ofRF CATV waveforms. The device's switch (560) may, for example, be usedto sort out digitally sampled legacy RF signals, and send these to adigital-optical to analog-electrical (RF) converter (600), thusproducing copies of the original legacy RF signals. The switch may alsobe used to sort out demodulated legacy QAM signals (waveforms) whichcontain the underlying QAM symbols, and send these QAM symbols to QAMmodulators (603), thus producing copies of the original legacy RF QAMsymbols by another method. The switch may also be used to handle IP datapackets from the IP backbone connected to the head end, and send theseto appropriate QAM modulators (e.g. edge-QAM modulators 607 or 604).This later is particularly useful for various video on demand and DOCSISapplications.

The QAM or OFDM modulator(s) may be part of a D-CMRTS/DOFN PHY unit, andat least more advanced embodiments of the D-CMRTS/DOFN may often havethe corresponding MAC and packet switching capability, as well as anoptional controller (e.g. microprocessor and associated software) toselect the appropriate portions of the digitally modulated opticalsignals (and wavelengths if necessary) and also control the packetswitching, MAC and PHY (including the D-CMRTS QAM modulators) units asneeded.

More advanced embodiments of the D-CMRTS/DOFN will also usually containat least one software controllable switch that can be remotely directed(usually by the controller (1102)) to select at least some of thedigitally encoded optical signals and direct the at least one D-CMRTSQAM modulator devices to encode the selected optically transmitteddigital data into various of RF QAM waveforms at a selected set offrequencies (remotely generated QAM signals). Often this softwarecontrollable switch will be part of, or be controlled by, an optionalprocessor or controller.

The D-CMRTS/DOFN may also contain at least one remotely softwarecontrollable RF packet processor capable of detecting upstream datacarried by CATV RF upstream signals generated by at least one cablemodem, and digitally repackaging and this upstream data and digitallyretransmitting this upstream data along the optical fiber.

The software controllable switch(s) and/or software controllable RFpacket processor(s) may optionally be capable of being remotelyconfigured by software (e.g. controller software (1102)) to implement atleast a subset of the standard DOCSIS upstream and downstream functions.For example, on the upstream side, one or more of the DOCSIS upstreamTime Division Multiple Access (TDMA) and DOCSIS Synchronous CodeDivision Multiple Access (SCDMA) functions may be implemented. On thedownstream side, one or more of the various DOCSIS QAM modulation modes,such as 16-level, 32-level, 64-level, 128-level, and 256-level QAMmodulation modes may be implemented. Depending upon the level offunctionality of the D-CMRTS that is desired, the D-CMRTS may, at thefiber node, generate QAM channels carrying digital broadcast video,digital video on demand, digital High Definition (HD) video, Voice data,and DOCSIS (data) channels.

As previously discussed in Ser. No. 13/674,936, and elsewhere, at leastsome embodiments of the CMRTS/DOFN units were disclosed as being capableof implementing additional functions that are not yet officially part ofthe DOCSIS specification (i.e. non-DOCSIS functionality), such asupstream data from various new models of non-DOCSIS standard set-top boxgateways, may also be implemented by the D-CMRTS/DOFN. Here addition ofadditional or non-standard functionality is facilitated by the fact thatthe present invention's virtual head end (1120) is highly configurable.Thus by merely implementing a software upgrade to the virtual CCAPcontroller software (1120), and by sending a software upgrade toreconfigurable DOFN (e.g. FPGA/DSP configurable DOFN), major upgrades inHFC system capability become quite feasible.

Here some of this optional non-standard functionality is discussed inmore detail. More advanced versions of the D-CMRTS/DOFN unit may beconfigured to implement additional functions that are not yet officiallypart of the DOCSIS specification (i.e. non-DOCSIS functionality). Thisadditional functionality can include ability to handle an increasedamount of upstream data from various new models of non-DOCSIS standardset-top box gateways. As another example, more advanced D-CMRTS/DOFNunits may be capable of more intelligently allocating the downstream QAMchannels depending upon data content need messages generated by moreadvanced set top boxes in various households. That is, if a householdneeds access to a particular video channel, for example, the household'sset top box may send a command to the local D-CMRTS/DOFN unit requestingthis channel. This channel may already be available to the D-CMRTS/DOFNunit because it has access to a vast stream of data from the opticalfiber connection, but in order to preserve scarce CATV bandwidth, thelocal D-CMRTS/DOFN unit will only allocate a CATV QAM channel for thisdata upon request. Other embodiments of the D-CMRTS/DOFN unit may alsobe capable of many other functions as well.

As another example, one persistent problem with CATV cable is that thesignal attenuation properties of the RF signals vary as a function offrequency, as well as the particular characteristics of that stretch ofcable. Lower frequency channels will degrade differently from higherfrequency channels. It is difficult, with the present “one size fitsall” scheme where all QAM channels at all frequencies are generated atthe cable head, to put out a standard CATV signal where all QAM channelsare modulated the same regardless of frequency. By contrast, since aD-CMRTS/DOFN unit may generate some or all RF channels (e.g. QAM RFchannels) locally, it is possible to use various software adjustableparameters to spectrally shape the various RF QAM waveforms to adjustfor the attenuation over frequency properties of the that neighborhood'sCATV cable. Thus in contrast to prior art methods, where often some ofthe lower or higher frequency channels have more noise, it will now bepossible to ensure that all channels have low noise, regardless of thefrequency of the channel.

Thus the present disclosure teaches methods that enable a cableprovider, over a series of gradual system upgrades as desired, toincreasingly be able to distinguish itself by being able to providecutting edge services that are ahead of its competitors. Various levelsof D-CMRTS/DOFN can be provided, from simple units designed for neartransparent upgrades of legacy HFC systems, to more advancedD-CMRTS/DOFN units that can handle either a superset of the DOCSISfunctions or a completely different set of functions, because it can beused to extend the functionality of the HFC system far beyond that ofthe standard DOCSIS functions. Additionally, as per the main focus ofthe present application, the legacy head end may be replaced by a moreefficient virtual head end.

Here the term “superset” is being used to denote the additional(non-standard DOCSIS) functionality. Thus, for example, a D-CMRTS/DOFNthat has enough backward compatibility to do either a full set of DOCSISfunctions or a subset of DOCSIS functions would be described asimplementing a DOCSIS “superset” if it also implements additionalnon-standard DOCSIS functions. Other examples of additional non-standardDOCSIS functionality (non-DOCSIS functionality) includes functionalityto transmit various forms of digital video such as standard digitalvideo, high definition HD digital video, and various forms of digitalvideo upon demand.

The various D-CMRTS/DOFN devices will usually have software controllableswitch(s) and software controllable RF packet processor(s), and willoften also incorporate their own microprocessors or microcontrollers, aswell as memory (such as flash memory, ROM, RAM, or other memory storagedevice) to incorporate software needed to operate the switches andprocessors, interpret command packets sent from the virtual shelfmanager, and transmit data packets to the virtual shelf manager.

For greater flexibility, the various D-CMRTS/DOFN devices may beconstructed using various software reconfigurable Field-programmablegate arrays (FPGA) and Digital signal processor (DSP) devices for theirvarious MAC and PHY units, as described in more detail in copendingapplication Ser. No. 13/555,170, “DISTRIBUTED CABLE MODEM TERMINATIONSYSTEM WITH SOFTWARE RECONFIGURABLE MAC AND PHY CAPABILITY”, thecontents of which are incorporated herein by reference. These FPGA andDSP units may be software reconfigured to enable various types of QAMand other modulation scheme transmitters and receivers, such as filterbank transmitters and filter bank receivers. These may be constructedfollowing the methods of Harris et. al., (“Digital Receivers andTransmitters Using Polyphase Filter Banks for Wireless Communications”,IEEE Transactions on Microwave Theory and Techniques, 51(4), pages1395-1412, 2003). Other alternative methods may also be used.

The D-CMRTS/DOFN units will also often have an RF combiner device, or atleast be attached to a combiner device (such as a Diplex or Multiplexdevice), that combines all of the various RF QAM and other CATV signalsto produce a combined RF signal suitable for injection into a CATV cableconnected to at least one cable modem. The diplex or multiplex devicemay also serve as a frequency splitter, or an adjustable frequencysplitter, directing some frequency ranges (e.g. 5-42 MHz for upstreamfunctions, and other frequency ranges (e.g. 54-870 MHz) for downstreamfunctions. These frequency ranges may be adjusted under software controlas desired.

Alternatively, this multiplex device may be external to the actualD-CMRTS/DOFN unit; however the D-CMRTS unit will normally depend uponeither an internal or external combiner (e.g. a diplex or multiplexdevice) for functionality.

As previously discussed, one particular advantage of the presentdisclosure's virtual CCAP or virtual head end is that when more advancedfunctionality is desired, it can often be implemented by upgrading thevirtual CCAP controller software (1102).

To do this, as previously discussed, because the prior art(non-dispersed functionally) CMTS units were often referred to as a“shelf”, the virtual CCAP controller software that controls thefunctionality of the virtual head end and the more advanced dispersedD-CMRTS/DOFN units of this invention will be referred to in thealternative as a “virtual shelf”. This “virtual shelf” software willideally manage the virtual head end (1120) as well as the dispersedD-CMRTS/DOFN system in a way that will be easy to manage, and ideallysometimes almost transparent, to the cable head operator, so that themore complex data distribution properties of the invention's dispersedD-CMTS-D-CMRTS system can be handled as if the system behaved more likea simpler, prior art, CMTS system.

For more advanced functionality, one important function of thecontroller computer processor and “virtual shelf” software (1120) willbe to select and control at least the digital optical signals and theremotely generated QAM signals or OFDM signals. These can be managed ina way that, as will be discussed, greatly increases the amount ofIP-on-demand data available for cable system users.

FIG. 1 shows an overall view of the various frequencies and datachannels allocated for prior art CATV systems (100). Typically the lowerfrequencies, such as 5-42 MHz, were allocated for use in transmittingdata “upstream” from the individual cable modems back to the Cable Head(102). Typically upstream data was transmitted using a time-share TDMA(Time Division Multiple Access) manner in which individual cable modemsare allocated certain times on roughly 2 MHz wide QAM channels totransmit data. Starting at around 54 MHz on up to roughly 547 MHz, spacewas allocated for legacy analog video channels (104), which transmit onroughly 6 MHz wide FDM channels. At frequencies above that, frequencies(space, bandwidth) was allocated for digital television transmitting onroughly 6 MHz wide QAM channels (106), and above that, space wasallocated for DOCSIS services (108) that may transmit voice, on-demandvideo, IP, and other information, again generally as a series of 6 MHzwide QAM channels. Above about 1 GHz, cable bandwidth is and was seldomused, although future services may extend further into this region.

The invention is indifferent as to the use of higher frequency cablebandwidth and channels. If available, the invention may use them. If notavailable, the invention will cope with existing cable frequencies andbandwidth.

Prior art CATV cable thus had a finite bandwidth of at most about100-200 downstream QAM channels, and a very limited upstream bandwidth.When this bandwidth is used to serve a large amount of differentcustomized types of data to a large amount of different subscribers,this bandwidth quickly becomes exhausted. Due to the extreme constraintson upstream bandwidth, upstream bandwidth quickly became limiting.

A drawing showing how the prior art CATV spectrum allocation can bedescribed in a more simplified diagram is shown below (110), (120). Thisdiagram will be used in various figures to more clearly show some of theCATV spectrum allocation aspects of the invention, as well as to showhow the invention may deviate from the prior art CATV spectrumallocation on occasion.

The “upstream” segment (112) is an abstraction of all prior art CATVupstream channels, including both presently used upstream channels inthe 5-42 MHz region. The “video” segment (114) is an abstraction of boththe almost obsolete prior art analog TV FDM channels, as well as thestandard “digital video” channels, as well as the projected digitalvideo channels that will occupy the soon to be reclaimed analogbandwidths once the analog channels are phased out. Segment (114) alsorepresents other standard digital radio and FM channels, and in generalmay represent any standardized set of downstream channels that willusually not be customized between different sets of users andneighborhoods.

The “DOC1” channel (116) may be (depending upon mode of use) either afull set or subset of present or future DOCSIS channels. As commonlyused in this specification, DOC1 often represents a basic set of DOCSISservices that would be made available for fallback use by neighborhoodsin the event of a failure of the higher performance IP/on demand or DOC2channels (118). The DOC1 QAM channels are normally chosen so as to notexhaust the full bandwidth of the CATV cable, so that at least someremaining QAM channels are available for the neighborhood customizedDOC2 channels. The “IP/On-demand or DOC2” channel (118) is essentially(depending upon mode of use) the remaining available downstreambandwidth on the CATV cable, and is usually reserved for transmittingneighborhood specific data (IP/On-demand data), often transported by adifferent communications media (such as a second fiber or secondwavelength, and often by a non-QAM protocol) from the cable head toindividual neighborhoods.

Note that when discussing prior art usage, the sum of the DOC1 (116) andIP/On demand (118) channels sent by optical fiber to a group ofneighborhoods can never (or at least should not ever to avoidinterference) exceed the effective bandwidth (i.e. the carrying abilityof the CATV cable and the ability of cable modems to detect the cable RFsignal) of the CATV cable.

By contrast, when discussing the invention, the sum of the DOC1 (116)and IP/On-demand (118) channels sent by optical fiber to a group ofneighborhoods will often exceed the effective bandwidth of the CATVcable on a group of neighborhoods basis, although the sum of DOC1 (116)and IP/On-demand (118) RF waveforms or signals will never exceed theeffective bandwidth of the CATV cable on a per-neighborhood basis.

If the same CATV spectrum is transmitted by optical methods (i.e.optical fiber), so that the same waveforms are transmitted at the samefrequency spacing, but simply transposed to optical wavelengths, thenthis spectrum will be designated as (120), but the various waveformswill otherwise keep the same nomenclature to minimize confusion.

Some embodiments, the invention may also intentionally deviate from thisprior art CATV spectrum allocation scheme. In particular, as will bediscussed, the amount of bandwidth reserved for upstream data may besubstantially increased. This may be done by, for example, deviatingfrom the traditional 4-42 MHz region reserved for upstream data, andallocating a larger number of CATV RF frequencies for upstream data.

FIG. 2 shows an overall view of the various wavelengths allocated forboth prior art optical fiber wavelength division multiplexing schemes,as compared to the dense wavelength division multiplexing (DWDM) methodswhich may optionally be used in some embodiments of the presentinvention. Here the optical fiber wavelengths being used at present(150) include a 1310 nm O-band wavelength (152) often used to transmitthe various CATV RF channels, such as the various QAM channels,modulated essentially according to the same CATV RF waveforms, but atoptical wavelengths according to scheme (120). Supplemental data isoften transmitted in the C-band around 1550 nm (154), often on opticalwavelengths and waveforms that, because the waveforms are modulatedaccording to non-optimal CATV waveforms, must be separated from eachother by a relatively large wavelength separation, and which carrysub-optimal amounts of data per wavelength.

By contrast, when, as in the present embodiment of the invention, alldata is transmitted according to the same digital format, such as an IPbased GigE format, then it becomes relatively simple to label any typeof data as to data type and data destination, dump it in the opticalfiber digital stream at the same optical wavelength (170), and thenextract the digital data at the other end of the optical fiber, sort bydata type and destination, and send it to the proper recipient. This alldigital approach thus can have substantial advantages over DWDM methodsbecause the DWDM costs of producing optical modulators (e.g. opticalfiber lasers) as well as demodulators, wavelength splitters, and thelike, thus can be reduced.

Although the present invention, by virtue of the fact that all data willusually be transmitted digital form over the optical fiber, thus doesnot require use of dense wavelength division multiplexing (DWDM)methods, it is useful to briefly examine such DWDM methods because theymake the advantages of the present invention's all digital approach moreapparent.

The Dense Wavelength Division Multiplexing (DWDM) concept is shown in(160), and is discussed in more detail by way of copending applicationSer. No. 13/555,170 and provisional applications 61/385,125 and61/511,395, the contents of which are incorporated herein by reference.These applications taught that backward compatible downstream legacysignals might be transmitted in analog form using, for example, a legacyO-band analog signal, and additional channels and services might betransmitted at multiple wavelengths using more efficiently modulateddata signals (such as one of the various optical fiber GigE protocols),for example as a series of closely spaced wavelengths (162). Theseprovisional applications also taught that due to the fact that becauseuse of prior art QAM, NTSC, FM waveforms and the like, when used onoptical fiber, is relatively inefficient, on a bits of data per unitbandwidth basis, compared to more modern digital methods of transmittingdata, use of digital signal transmission methods offered compellingdifferences in data transmission rates.

Specifically, whereas prior QAM, NTSC, FM waveform methods might, forexample, be used to transmit 4 C-band wavelengths, each carrying about 6gigabits per second of data, using CATV compatible QAM, NTSC, FMwaveforms (154), by switching to digital methods, much higher datarates, such as up to 80 wavelengths of C-band data (162), each carrying10-100 gigabits of data per second, are possible using more efficientoptical fiber signal modulation methods.

The present invention thus builds on this earlier insight, and is basedon the further insight that by completely digitizing all optical fibertraffic (e.g. removing the legacy analog waveform optical fibertraffic), intelligently compressing as possible (e.g. using QAM symboldemodulation methods) and going all digital, then on a bits per secondbasis, much more data may be transmitted using fewer opticalwavelengths, thus saving the costs of the extra equipment needed tohandle the extra optical wavelengths.

Note however that the present invention still may make use of DWDMmethods when, for example, extremely high data transmission rates (bitsper second) are desired. However in the present invention, use of alldigital optical fiber transmission is now the preferred embodiment, anduse of DWDM methods is an optional element that is not required topractice the invention, although it may be.

To help visualize how switching to an all digital optical fibertransport format can help transmit more data over even a single opticalfiber wavelength, the simplified digital transmission diagram (170) or(306) is frequently used. Note that a legacy O band analog modulatedoptical signals (152) or C band optical signals (154) can carry only atmost about 6 Gigabits per second (Gbit/s), with an effective bit ratemuch less than this due to the inefficiencies of the analog format. Bycontrast, the more efficient digital format can transmit 10, 40, 100,1000 or more Gbits/second or more at the same wavelength, and here theeffective bit rate is very close to the theoretical bit rate. The neteffect is that by switching to an all digital mode, the same wavelengthon the optical fiber can now transmit much more data than it couldearlier.

FIG. 3 shows a simplified version of how prior art HFC systems (200)transmit data from the legacy cable head (202) to different opticalfiber nodes (204) serving different neighborhoods (206). Eachneighborhood will typically consist of up to several hundred differenthouses, apartments, offices or stores (208) (here referred togenerically as “houses”), each equipped with their own cable modems (notshown). Here, for simplicity, only the downstream portion of the HFCsystem is shown.

The legacy cable head will generally be connected to an IP backbone(212) and/or will obtain standardized media content (210) (such as astandard assortment of analog and digital video channels) from one setof sources, and also obtain more individualized data (212), such asvideo on demand, IP from the IP backbone which may include both theinternet, and other individualized data from other sources. This data iscompiled into a large number of different QAM (and at present also FDM)modulated CATV broadcast channels at (214). The CMTS shelf, shown herealso (214) will often have a number of different blade-like line cards(216) The various QAM channels and IP data are combined and aretransmitted by optical fibers (218) to different areas (groups ofneighborhoods).

Note that the FDM modulated CATV broadcast signal is an NTSC analogsignal (for older style analog televisions), and even the QAM signal,although it carries digitally encoded information, is itself an analogsignal as well. For historical reasons, in the downstream direction,both FDM/NTSC and QAM waveforms (signals) usually have a bandwidth ofabout 6 MHz in the US.

To show this, as previously discussed in FIG. 1, the FDM/NTSC and QAMsignals are shown as having a center wavelength and bandwidth in orderto emphasize the essentially analog nature of this signal, even whencarrying digital information. These analog signals can be carried byoptical fibers, and converted into RF signals for the CATV cable part ofthe network, using very simple and inexpensive equipment.

As previously discussed, typical HFC networks actually have a rathercomplex topology. Rather than sending one optical fiber from the CTMS toeach different neighborhood, typically optical fibers will servemultiple neighborhoods. To do this, the signal from the CTMS sideoptical fiber will at least usually be split (by an optical fibersplitter (220)) into several different optical sub-fibers (222), andeach sub-fiber in turn will in turn carry the signal to a differentfiber optic node (fiber node, FN) (204). Here the rather complex ringtopology of HFC networks will be simplified and instead represented bythese fiber splitters.

At the fiber node (FN) (204), the optical signal is converted into aCATV radio frequency (RF) signal and sent via CATV cables (226) toindividual cable modems at individual houses (208) in each neighborhood.Typically each neighborhood will consist of 25 to several hundredhouses, served by a CATV cable (226) that connects to the local fibernode (204).

Since the CATV cable (226) is connected to all of the houses (208) inthe neighborhood (206), if the cable modem in one house in aneighborhood wants to request customized on-demand video or IP, then allof the houses in the neighborhood that are attached to that particularCATV cable will actually receive the customized signal. Although onlythe cable modem associated with the requesting house (not shown) willactually tune into and decode the requested signal, it should beappreciated that if each individual house in the neighborhood were tosimultaneously request its own customized set of video on demand or IPat the same time, the limited bandwidth of the CATV cable would berapidly saturated. As a result, there is an upper end to the amount ofcustomized data that can be transmitted to each house, beyond whichbandwidth must be limited and/or requests for additional customized datawill have to be denied.

Although the different blades or line cards (216) of the CMTS shelf(214) at the legacy cable head (202) can send different customizedIP/on-demand channels to different groups of neighborhoods, thegranularity of this process is sub-optimal, because all individualneighborhoods connected to the same fiber splitter will get the samecustomized IP/on-demand signal. Given the limited bandwidth of the CATVcable, if all neighborhoods get the same signal, then the amount of datathat can be sent to each individual neighborhood must, by necessity, belimited so as not to exceed the total available bandwidth.

FIG. 4A shows an overview of how one aspect of inventor's art may beused to upgrade a legacy analog optical fiber (222) based HFC CATV cablesystem (still using a legacy head end) by replacing the analogmodulators (201) and demodulators (300,304) on either end of the systemwith digital demodulators (399) and remodulators (300,304), where herethe remodulators are generally embedded into the DOFN (300,304) as thevarious QAM modulators (712) and the like. The DOFN are connected to theoptical fiber (222) on one side, and the neighborhood CATV cable system(226) on the other side. The neighborhood CATV system in turn connectsto various households (208) as before, and also may contain variousactive devices (290) such as amplifiers to boost the RF signals, and thelike. The legacy head end of the CATV system (202) is here abstracted asa device that generates a plurality of downstream RF waveforms/signals,such as QAM signals (106).

FIG. 4B shows a more detailed overview of how the invention may be usedto upgrade a legacy analog optical fiber based HFC CATV cable system,still using a legacy head end, that is was transmitting a mixture ofconsisting of a plurality of video QAM channels (106) and IP data (108),such as DOCSIS IP data. Here the legacy QAM channels (106) may bedemodulated into their underlying QAM constellation symbols by converterdevice (399). This QAM symbol data, along with the legacy IP data (108),can be encapsulated by the converter device (399) into various digitaloptical data packets, and transmitted over the optical fiber (222) inthis more efficient digital form. At the optical fiber node (300 a), thedata packets can be parsed, and the QAM or other RF channels regeneratedby remodulated by using the QAM constellation symbols or OFDM symbols todrive various optical fiber node QAM RF modulators/transmitters, such as(712). The IP data can also be extracted from the optical data packets,and used to feed an optical fiber node based CMTS system.

In this context, “encapsulate” means to package the data bits, bytes, orother bit oriented format from the relevant input into data packets,such as Ethernet data packets or frames, along with appropriate headers,checksums, source information, destination information, and otherappropriate control information. Thus using QAM waveforms as an example,the data will be QAM constellation symbols, usually as part of theEthernet frame/packet payload. In addition to standard Ethernet framestructure data, this payload data may additionally contain informationabout the relative position or timing that the QAM symbols have in theQAM waveform, the source of the QAM waveform (e.g. what channel), thedestination channel, and even information as to intensity of the QAMwaveform, QAM waveform pre-distortion, echo cancellation, and the likeas needed to help correct for distortions in the CATV cable, as percopending patent application Ser. Nos. 13/400,415 and 13/478,461, thecontents of which are incorporated herein by reference. Once the datapackets are received, the QAM symbol data or other data can beextracted, and the source information, destination information, andother appropriate control information then used by the system to thenproperly use the QAM symbol data to accurately reconstruct the properQAM waveforms or other type waveforms as is best suited for the use athand.

Thus one aspect of inventor's art provides a method of upgrading alegacy Hybrid Fiber Cable (legacy HFC) system, previously configured totransmit data downstream over an optical fiber using analog optical QAMwaveforms, to a digital HFC system configured to transmit datadownstream over the optical fiber using digital optical transmissionmethods. Here, as previously discussed, the legacy HFC system willgenerally comprise a legacy head end configured to produce downstream RFQAM waveforms, and a legacy fiber optic transmitter system configured totransduce the RF QAM waveforms into downstream analog optical QAMwaveforms to be transmitted downstream to at least one legacy opticalfiber node. The legacy HFC system will also generally comprise at leastone legacy optical fiber node is configured to receive the downstreamanalog optical QAM waveforms, transduce the analog optical QAM waveformsinto RF QAM waveforms, and transmit these RF QAM waveforms downstreamover the at least one set of neighborhood CATV cables.

To upgrade this system, the legacy fiber optic transmitter system (201),which is generally attached in between the CATV PHY (614) and theoptical fiber cable (218), can be replaced with a digital fiber optictransmitter system (399) configured to transmit at least one downstreamQAM channel over the optical fiber as a plurality of QAM constellationsymbols by demodulating the QAM waveforms, extracting the QAMconstellation symbols encapsulating the QAM constellation symbols into aplurality of Ethernet frames or other digital transmission formatframes, and digitally transmitting this plurality of Ethernet frames orother digital transmission format frames over the optical fiber.

The conversion will also generally require that at least one legacyfiber optic node (204) be replaced with a digital optical fiber node(DOFN) (300,304) configured to receive this plurality of Ethernet framesor other digital transmission format claims, extract these downstreamQAM constellation symbols, and use these downstream video QAMconstellation symbols to modulate at least one DOFN QAM modulator, thusproducing downstream QAM RF signals.

Here the downstream QAM channels will generally comprise either videoQAM channels, video Edge-QAM channels, or IP-QAM channels.

In some cases, as described in more detail elsewhere, the downstreamdata may further comprise either legacy RF waveforms, such as NationalTelevision System Committee (NTSC) or more advanced DOCSIS 3.1waveforms, such as Orthogonal Frequency Division Multiplexing (OFDM) RFchannels. In these situations, the system may further handle thesenon-QAM signals by, for example:

1: digitally sampling the NTSC or OFDM RF channels at the head end,producing a plurality of digitized waveform data, encapsulating thisdigitized waveform data into a plurality of digitized waveform datacontaining Ethernet frames or other digital transmission frames, anddigitally transmitting this plurality of digitized waveform datacontaining Ethernet frames or other digital transmission framesdownstream over the optical fiber (222). There, at the DOFN (300,304),the system may receive this plurality of digitized waveform datacontaining Ethernet frames or other digital transmission frames, extractthis plurality of digitized waveform data, and use this plurality ofdigitized waveform data to drive at least one digital to analogconverter, thus producing downstream NTSC or OFDM RF channels which inturn can be injected into the neighborhood CATV cables (226).

In the case where the downstream data may be composed of more advanced(e.g. DOCSIS 3.1) Orthogonal Frequency Division Multiplexing (OFDM) RFchannels, these OFDM RF channels may be digitally transmitted bydemodulating the OFDM RF channels at the head end (399), producing aplurality of OFDM symbols, encapsulating this plurality of OFDM symbolsinto a plurality of OFDM symbol carrying Ethernet frames or otherdigital transmission frames, and digitally transmitting these OFDMsymbol carrying Ethernet frames or other digital transmission framesdownstream over the optical fiber (222).

In this case, the DOFN (300,304) can be configured to receive thisplurality of OFDM symbol carrying Ethernet frames or other digitaltransmission frames, extract this plurality of OFDM symbols, and usethis plurality of OFDM symbols to drive at least one OFDM RF modulator,thus producing downstream OFDM RF channels, and also inject these OFDMRF channels into the local neighborhood CATV cable system (226) as well.

In this approach, the upstream transmission methods generally areconsistent with the above discussed downstream methods. Here, forexample, when upstream transmission of RF QAM channel data waveforms orany upstream RF channel data waveforms or desired, the DOFN (300,304) or(300 a) may be configured to, for the case of upstream RF QAM datacarrying waveforms, receive the upstream RF QAM channel waveforms,demodulate these upstream RF QAM channel waveforms into a plurality ofupstream QAM constellation symbols, and encapsulate this plurality ofupstream QAM constellation symbols into a plurality of Ethernet framesor other digital transmission format frames. The DOFN (300,304), (300 a)can then use the optical fiber (222) to digitally transmit thisplurality of Ethernet frames or other digital transmission format framesupstream to the legacy head end (202) as assisted by converter (399) andadditional legacy head end extender equipment (500). Similarly forupstream RF OFDM channel data, the DOFN (300), (300 a) can be configuredto receive the upstream RF OFDM channel data waveforms, and demodulatethe RF OFDM channel waveforms into a plurality of upstream OFDM symbols.The DOFN can then encapsulate this plurality of upstream OFDM symbolsinto a plurality of Ethernet frames or other digital transmission formatframes and transmit upstream on optical fiber (222) as describedpreviously.

In the case where the upstream data are other types of RF waveforms (orwhere desired for QAM and OFDM upstream waveforms as well), as anotheralternative, the DOFN can be configured to receive the upstream RFchannel data waveforms, and digitally sample these RF channel datawaveforms producing a plurality of digitized waveform data. Then asbefore, the DOFN can encapsulate this digitized waveform data into aplurality of Ethernet frames or other digital transmission frames, andtransmit upstream on fiber (222) to the legacy head end (or for thatmatter the invention's improved virtual head end) as before.

The process of migrating from a legacy analog-signal over optical fiberHFC CATV system to an improved digital signal over optical fiber HFCCATV system can take place in various phases or increments. At thesimplest upgrade phase or increment, here called phase 1, the legacyhead end (202) is left in place, any prior art DOCSIS and CMTSfunctionality can be left intact, and only the video QAM waveforms sentdownstream over the optical fiber from the head end to the variousoptical fiber nodes needs to be demodulated into QAM constellationsymbols, encapsulated or packaged into suitable digital optical packetssuch as various Ethernet packets, and sent downstream to improved DOFNoptical fiber nodes that in turn can extract the various QAMconstellation symbols from the digital optical fiber data packets. TheseDOFN fiber nodes can then use these QAM constellation symbols, togetherwith various DOFN QAM modulators, to reconstruct the original head endQAM waveforms as RF QAM waveforms, and then send these downstream overthe local neighborhood CATV cable.

In an alternative upgrade phase or increment, here called phase 2, thelegacy head end is again kept in place, and both the demodulated QAMconstellation symbols from the various video QAM channels and thevarious IP data (e.g. DOCSIS IP data, originating from head end CMTSunits) can be encapsulated or packaged into suitable digital opticalpackets, and be sent downstream over the optical fiber. The DOFN willalso preferably be configured to return any upstream data over theoptical fiber using digital protocols as well.

In a still a still later upgrade phase or increment, here called phase3, the cable head end need no longer be configured to generate QAM RFwaveforms. In other words, the legacy head end is no longer required.

In a first implementation of a non-legacy head end, the cable head endcan be still further simplified, and can for example translate videodata directly into digital data, such as QAM symbol data, but head endQAM modulators are no longer needed. Instead the cable head end can beessentially “all IP” or all digital. One advantages of the methodsdescribed herein is that the DOFN needed to implement phase 1 or phase 2of the upgrade can still be used for the phase 3 upgrades as well, thusenabling the upgrade process to proceed in various incremental steps asbudgets and user needs dictate.

In a second implementation of a non-legacy head end, the invention'svirtual head end or virtual CCAP methods may be used. These methods willbe discussed in more detail shortly.

Upgrading from an analog optical fiber system to a digital optical fibersystem has numerous advantages. In addition to the advantages discussedelsewhere in the specification, there are other advantages as well.

In contrast to analog transmission, which requires high linearitycomponents and signal transmission methods, and where at every signalcombining step, (which generally also requires an amplification step aswell) the noise floor level of the analog signal will generally rise,digital methods are generally superior:

1: Digital signal transmission methods can generally avoid non-linearityartifacts, such as cross-talk, that can corrupt signals.

2: Digital methods generally operate with a lower noise floor.

3: Digital methods generally produce higher level signals with improvedsignal to noise rations.

Particularly for optical fiber methods, where lasers used to transmit orto drive the optical fiber signals have limitations, such a requirementthat the laser not be overdriven. Thus to avoid this, the various analogwaveforms are driven at a lower intensity, and thus at varioussubsequent steps such as upon being the optical signal being receivedand demodulated, further amplification is needed, which in turnincreases the noise floor still further. By contrast, various digitalsignal protocols optimized for optical fiber can avoid these effects.

As a result, by switching to using digital signal transmission protocolsover optical fiber, the overall power requirements of the system canalso be reduced. The optical fiber lasers don't need to be operated inas high a linearity mode, and thus can be biased with a smaller amountof current, reducing transmitter power utilization. Further the need forpower amplifiers, which often add about 10-12 watts of power utilizationper amplifier, is also reduced. Thus in addition to the advantages ofhigher data throughput and more flexibility discussed elsewhere in thisspecification, there are also advantages of lower power utilization, andlower noise levels (i.e. less digital signal corruption due to noise).

Various optical fiber digital transport protocols may be used for suchdigital over optical fiber transmission purposes. In some embodiments,it may be useful to select a protocol from the set of various IEEE 802.3high speed Ethernet protocols, such as IEEE 802.3ba, IEEE 802.3bm, IEEE802.3bg, IEEE 803.3z and the like. Here, depending on the legacy opticalfiber in use, longer distance capable single-mode optical fiber (SMF)methods, such as 40GBase-LR4, 100GBase-LR4, or 100Gbase-ER4, 1000Base-X,1000Base-SX, 1000Base-LX, 1000Base-LX10, 1000Base-EX, 1000Base-ZX,1000Base-BX10 and other methods may also be used. If the legacy analogoptical fiber is going to be used without substantial upgrades, then useof digital protocols that are compatible with the wavelengths used bythe analog optical fiber, such as commonly used 1310 nanometer legacy Oband wavelengths (e.g. 1000Base-LX, 1000Base-LX10 or 1000Base-EX) may bepreferable. If use of alternative wavelengths, such as the C bandwavelengths (e.g. 1550 nanometer wavelength) is preferred, then use ofalternative protocols such as 1000Base-ZX may be preferable. Many otherprotocols, such as 1000Base-BX10 may also be used.

FIG. 4C shows still more detailed view of how applicant's art may beused to upgrade a legacy analog optical fiber based HFC CATV cablesystem that is was transmitting a mixture of consisting of a pluralityof legacy video QAM channels, other analog RF channels such legacy NTSCvideo channels, and legacy IP data, such as DOCSIS IP data. Here, anumber of the various components are further identified using thenomenclature used for FIG. 7, and it may be useful at this time tocompare FIG. 4C to FIG. 7, since the two figures are highly related.

Here, as before, if a legacy head end is being used, the legacy videoQAM channels (106) may be demodulated into their underlying QAMconstellation symbols using a demodulator device in converter unit (here399 b). The other RF video channels (104) may be handled by digitizationand optional compression, as desired, using appropriate analog todigital converter circuitry in converter unit (399). OFDM RF channelsmay also be handled by suitable demodulators or digitizers, as desired(not shown). This QAM symbol data, digitized RF channel data and thelegacy IP data, can be encapsulated into various digital optical datapackets, and transmitted over the optical fiber (222). At the DOFNoptical fiber node (here shown as 300 b and also as 304) the datapackets can be parsed (560), and the QAM channels regenerated orremodulated by using the QAM constellation symbols to drive variousoptical fiber node QAM RF modulator/transmitters (603). The digitizedanalog RF channels (which can optionally be decompressed) arereconstituted by feeding them into an electrical system comprising adigital to analog converter (600) to regenerate the analog RF channels.The IP data signals are selected and converted in to the appropriateCATV waveforms by the DOFN's CMTS/CMRTS unit. The three types of RFwaveforms can then be combined (606) and injected into the neighborhoodCATV cable system (226) as before.

FIG. 4D contrasts the difference in downstream data transmission betweena prior art HFC system that operates using an optical fiber carrying ananalog CATV modulated 1310 nm wavelength signal, and the invention'simproved digital methods using digital (Ethernet) modulated signals orother optical fiber optimized digital signal formats.

In the prior art system, the conversion process between the opticalfiber (222) and the CATV cable (226) that occurs with a typical priorart fiber node (204) is shown, and contrasted with the invention'simproved D-CMRTS fiber node (300,304). Here, for simplicity, only thedownstream portion of the process is illustrated.

In the prior art conversion process (top), the optical fiber (222)carries both the standardized video signals, and the analog QAM signal(that contains digital information) for both digital television andDOCSIS use (that can carry on demand video or IP data).

The prior art “dumb” fiber node (204) simply converts the opticalfiber's optical FDM or QAM analog signals into RF FDM or QAM signals andpasses these signals to the CATV cable (226). Thus if, for example,there are four different CATV cables connecting to this different fibernode, all will get the same customized IP/On-demand signal, and this inturn may be rather inefficiently transmitted to potentially thousands ofnon-target households that did not request the customized signal.

By contrast, by using the invention's improved “smart” D-CMRTS/DOFNfiber nodes (300,304), any legacy standardized signal (e.g. thestandardized video channels) and (for backwards compatibility) either afull set or subset of the DOCSIS QAM channels are first digitized andtransmitted by the optical fiber in a digital format. This digitalformat makes it easy to add additional (non-legacy) data (e.g. video onthe demand, DOCSIS superset services) and transmit this additional dataon the same optical fiber wavelengths used to transmit any legacy CATVdata.

If legacy data is transmitted over the optical fiber, it may optionallycarry a digitally encoded version of the legacy CATV spectrum, which canbe reconstituted (320) into analog format at the D-CMRTS unit into RFQAM waveforms and other waveforms that may optionally be injected intothe CATV cable (120) for fallback or legacy operation.

To emphasize the fact that the optical fiber is often carrying data bynon-CATV-compatible or QAM signal carrying methods, the signal carriedby the D-CMRTS fiber is shown as a series of lines (306) to symbolizethe fact, that alternative digital (e.g. GigE) methods of signaltransmission are being used. Here each line (306) represents a differenttype of data stream to different node addresses or different nodechannels or CATV waveforms, some of which will ultimately will beconverted to a QAM signal and sent to a specific neighborhood.

At the invention's improved D-CMRTS/DOFN fiber node (300,304), in moreadvanced embodiments, the fiber node's CMRTS unit may additionallydetermine (or at least select) which set of customized data carried bythe various optical fiber digital packets (307, 308, 310, 312) isintended for that particular D-CMRTS and neighborhood, and retrieve thisinformation from the fiber. This information will then be QAM modulatedand converted to the appropriate RF frequency, put onto a suitable emptyIP/On-demand QAM CATV cable channel (314), (316), (318), and then sentby CATV cable to the neighborhood that requested that particular data.At the neighborhood, the particular cable modem from the house thatrequested that data can tune into this QAM channel and extract the data,while the other cable modems also attached to that cable will ignore theQAM channel and/or ignore the data.

As can be seen, the digital data packets (306) carrying different typesof data can be selected and put onto the CATV cable in various mix andmatch combinations (316), (318) as desired. Here for example, one RF QAMchannel on (316) came from optical fiber data packet type (310), two RFQAM channels came from optical fiber data packet type (312), and one RFQAM channel came optical fiber data packet type (308). By contrast, for(318), two RF QAM channels came from optical fiber data packet type(310), one RF QAM channel came from optical fiber data packet type(308), and one RF QAM channel came from optical fiber data type (312).By contrast, (314) illustrates the CATV channel coming from aneighborhood that is operating in legacy mode, where all channels camefrom optical fiber data packets from digitally sampled or demodulated(320) legacy RF signals (120) that were simply transported, in digitalformat, as is and then reconstituted (320) back to the originalwaveforms at the D-CMRTS fiber node (300,304), or alternatively by asimpler optical digital to RF analog converter type optical fiber node.

As will be discussed shortly, this method allows for much finergranularity, and a correspondingly higher rate of transmission ofcustomized data.

As previously discussed, in more advanced embodiments, the upstream datatransmission bottleneck at the CATV cable may be also addressed by anupstream CATV bandwidth reallocation scheme (See FIG. 10, (390)). Here,the amount of CATV RF spectrum allocated to upstream data transmissionmay, for example, be increased—e.g. from the original 5-42 MHz range upto, for example, 5-547 MHz or other higher upper value.

FIG. 5 shows an overview of one embodiment of the invention in operationin downstream mode. Here, in this embodiment, the improved “smart”D-CMRTS/DOFN fiber nodes (300,304) can transport a higher effectiveamount of customized user data. Here these improved “smart” D-CMRTS/DOFNfiber nodes (300,304), may in some embodiments, work in conjunction withan optional improved D-CMTS shelf and improved D-CMTS line cards at thecable head (see FIG. 7, 500).

In this embodiment, any legacy CATV RF waveforms, such as QAM waveforms(120), produced at the legacy head end (202) may be digitized by aconverter unit (399) and then injected into the optical fiber (301).This converter unit (399) may function by, for example, being configuredto accept at least one of downstream RF waveforms and downstream QAMchannels from the legacy head end, sample and digitize the downstream RFwaveforms (e.g. using simple high speed analog to digital conversion)and/or demodulate the downstream QAM channels into QAM symbols,producing downstream digital QAM symbols. In this embodiment, theconverter (399) is then digitally encoding the digitized legacy datainto a suitable optical fiber digital transport format, such as GigEdata packets, and then injecting these data packets into optical fiber(301) along with other data.

In the prior art system example previously shown in FIG. 3, an opticalfiber (218) from the prior art CMTS unit (214) at the cable head wassplit at by a fiber splitter (220) into three sub-optical fibers (allcarrying the same data) (222), and these sub-optical fibers were thenrouted to three different neighborhoods. Because all optical fiberscoming from the fiber splitter will carry the same data, all data,including customized data, is inefficiently sent to all threeneighborhoods, even though only one house from one neighborhood may haveactually requested the customized data.

As a result, the limited carrying capacity (bandwidth) of the prior artCATV cable system rapidly becomes saturated.

By contrast, by using a legacy head end (202) supplemented by animproved head end D-CMTS shelf (500) with improved D-CMTS line cards,and the inventor's digital transmission methods, larger amounts ofdownstream data can be sent even while using the same number of priorart optical fiber wavelengths. Again, the key concept is to use moreefficiently modulated optical fiber digital data transport protocols,such as higher data capacity GigE modulation protocols (304). Howevereven more improvements, particularly on the head end, are possible.

On the way to the various neighborhoods, or at the variousneighborhoods, the optical fiber cable and/or CATV cable data signalsmay optionally pass through a digital switch (220D). Here the inventor'sall digital transmission methods provide advantages over the previouslyproposed DWDM methods.

Under DWDM methods, data to different optical fiber nodes, or multipleoptical fiber node devices, might be transmitted at differentwavelengths, requiring that the switch (220) be a smart fiber splitterthat might, for example, incorporate rather expensive optical devices,such as software controllable Brag filters, that would operate toseparate out the various optical fiber wavelengths and divert them todifferent neighborhoods as needed.

By contrast, by using digital transport methods, digital switch (220D)can be a relatively inexpensive multiple port switch that operates todirect the various digital data packets to their respective destinationsaccording to digital data packet headers, and the like.

To do this, typically the various DOFN or D-CMRTS units will have aprocessor, memory, and at least one address (e.g. the specific nodeaddress, and or one or more alternate addresses such as the address of agroup of nodes, useful for when broadcasting the same signal to multiplenodes is desired). The DOFN or D-CMRTS units will typically beconfigured to process downstream digital data that is directed to theirrespective addresses.

Here, also, the IP data packets (e.g. digital samples of downstream RFwaveforms, downstream digital QAM symbols, or downstream digital IPdata) transmitted over the optical fiber will often have a specific(e.g. individual node or group of nodes) digital optical fiber nodeaddress.

In some embodiments, digital switch (220D) may be a multiple port switchdisposed either at the head end or else somewhere between the head endand the various digital optical fiber nodes (D-CMRTS units). This switch(220D) can thus be configured to read the specific digital optical fibernode or D-CMRTS addresses; and direct any of the various digital samplesof downstream RF waveforms, downstream digital QAM symbols, ordownstream digital IP data to the specific digital optical fiber node ornodes corresponding to their specific digital optical fiber nodeaddress, be it individual node address, or specific group of nodesaddress.

Here, use of all digital methods also helps cost reduce the variousD-CMRTS/DOFN costs. Whereas under the prior DWDM scheme, the variousD-CMRTS units themselves may have extracted data from multiple opticalfiber wavelengths through use of more expensive wavelength splitters(such as software controllable Brag filters), use of digital datapackets makes use of such wavelength splitters optional. Under thepresent all digital scheme, the various D-CMRTS units can essentiallypick and choose what GigE formatted data they may need from the overalldigital data packet stream (306, 307, 308, 310, 312) extract this data,reconstitute, remodulate, or QAM modulate the various data types, andthen output CATV RF signals (again often QAM channels) that can be acomposite of the data originally carried on the different digital datastreams (307, 308, 310, 312).

This “mix and match” process is symbolized by the various dark, dashed,and dotted parabolas shown in (316) and (318), which symbolize the CATVRF modulated data that is being output in neighborhood 1 andneighborhood 2 by D-CMRTS Fiber Node 1 and DCMRTS Fiber Node 2. Here forexample, as before, the downstream CATV data (226), (316) onneighborhood 1 is shown as a mix of dark parabolas (data originallyobtained from fiber digital data packets (310), a mix of dashedparabolas (data originally obtained from fiber digital data packets308), and dark dotted parabolas (data originally obtained from fiberdigital data packets 312). Note that the mix of data for neighborhood 2(318) is different from neighborhood 1. Whereas neighborhood 1 only tooka small amount of data (dark parabola) from fiber digital data packets(310), and a larger amount of data (two dark dotted parabola) from fiberdigital data packets (312), here the D-CMRTS/DOFN unit (300,304) forneighborhood 2 has selected more data (two dark parabolas) from fiberdigital data packets (310), and less data from (one dark dottedparabola) from fiber digital data packets (310).

Note also that the D-CMRTS/DOFN unit has freedom to decide whatfrequencies will be used to transmit this data over the CATV cables.Here the D-CMRTS/DOFN units determine what data to place on theneighborhood CATV cables based upon commands sent upstream by thevarious household devices attached to the CATV cable, and/or commandssent from the cable head (either upgraded legacy cable head, or thepresent improved virtual cable head). As previously discussed, in moreadvanced embodiments the D-CMRTS/DOFJ optical fiber nodes will besoftware controlled.

In more advanced embodiments, due to this software controllable,neighborhood specific (or at least neighborhood region specific) abilityto combine and repackage huge amounts of GigE formatted data carriedover a large number of optical fiber channels, the downstream capabilityof the system can now be substantially higher than prior art HFCsystems.

If, during a conversion process to the improved virtual head end of thepresent invention, it was desired to that some backward compatibility bepreserved, if desired, this can be done. Here the legacy head end can bepreserved for a time, and the fiber digital data packets (307) can stillbe used to digitally transmit the legacy CATV RF signals, such as QAMsignals. This can be done by having converter (399) intercept the legacysignals, digitize them by relatively simple Analog-RF to Digital Opticalunits, or by demodulating the QAM waveforms, extracting the QAM symbols,and then transmitting the QAM symbols in a digital format.

These digitized legacy signals can continue to be sent to “dumb” or“legacy” optical fiber nodes (204), and the digital optical datareconstituted (e.g. by optical-digital to analog-RF units, or by feedingthe digital QAM symbols into local QAM modulators). Both operations canbe done with minimal onboard intelligence at the optical fiber node,hence the “dumb” label. This “dumb” optical fiber

In FIG. 5, which still shows a legacy cable head in use, neighborhoods 1and 2 are served by the invention's improved “smart” D-CMRTS/DOFN fibernodes (300,304). By contrast, neighborhood 3 is only served by a “dumb”legacy fiber node (204). This legacy fiber node may operate by simplyconverting analog optical fiber waveforms into their corresponding RFwaveforms.

FIG. 6 shows one embodiment of the invention operating to send dataupstream. As previously discussed, at the CATV cable, considerably moreupstream data can be sent due to the previously discussed (but optional)methods of allocating more CATV bandwidth for upstream data (e.g. usingspectrum reallocation). Because spectrum reallocation is easier to draw,this larger amount of upstream data being transmitted along the CATVcable is symbolized here by the two dark dotted or dashed parabolaslabeled “upstream data” for neighborhoods 1 and 2, showing the higheramounts of upstream spectrum. By contrast, the smaller amount ofupstream data that can be transmitted using prior art methods issymbolized by the one dark parabola labeled “upstream data” forneighborhood 3. Here for example, perhaps neighborhood 3 is using thestandard US CATV upstream partition that allocates 5-42 MHz for upstreamdata, while neighborhoods 1 and 2 are using an alternate scheme such asallocating 5-85 MHz for CATV upstream data. Here for example, RF handler(606), which can have the functions of combining, splitting, orduplexing the various RF signals can be switched into an alternate modethat deviates from the present 5-42 MHz upstream and 54-870 MHzdownstream standards, and instead allocates the 5-85 MHz region forupstream, and for example the 92-870 MHz region for downstream.

As previously discussed, if the higher amount of upstream data wassimply transmitted back along the optical fiber system using the sameinefficient (for optical fiber) CATV signal modulation scheme (againusually QAM modulation), then the optical fiber itself would rapidlybecome a rate-limiting bottleneck. To avoid this problem, according tothe invention, the D-CMRTS/DOFN nodes extract this upstream data, andrepackage it into more efficiently (for optical fiber) modulated GigEformats. Additionally or alternatively, according to the invention,digital switches (220D) or smart fiber combiners (220) may themselvestake the upstream data sent by the optical fibers (222) connectingvarious neighborhoods, and extract the upstream data and repackage theupstream data in a more efficiently modulated (for optical fiber) GigEformat.

Although much of the upstream content consists of relatively standardQAM waveforms, at least some legacy CATV systems can also provide avariety of unusual upstream RF waveforms, such as various QPSK channelsfrom various older set top boxes, OFDM waveforms, such as used forDOCSIS 3.1, and the like. However it is burdensome to try to parse eachand every possible upstream waveform for content. To avoid this burden,here again more general methods that simply digitize whatever waveformis seen can be useful.

Thus to be able to digitize, and optically transport upstream, apossibly wide variety of possible RF CATV waveforms, while at the sametime trying to conserve optical fiber bandwidth where feasible, in someembodiments, the digital optical fiber node (D-CMRTS unit) mayadditionally have at least one of:

1: An RF digital converter device configured to accept upstream RFwaveforms transmitted over the CATV cable, and digitize these upstreamRF waveforms using, for example, a high speed analog to digitalconverter, and produce digitally encoded upstream RF channel data.

2: Since many upstream RF signals will be QAM waveforms, for opticalfiber bandwidth efficiency purpose, it is often desirable to also havean RF demodulator device configured to accept upstream RF QAM channelstransmitted over the CATV cable, and demodulate the RF QAM channels andproduce the upstream digital QAM symbols that originally were used toconstruct the various upstream QAM waveforms. The same can also be donefor OFDM waveforms as desired.

3: Additionally, for high performance, it is also often desirable tohave a QAM to IP conversion device configured to accept upstream digitalIP data packets transmitted by the upstream QAM RF channels over theCATV cable, and extract the upstream digital IP data packets, thusproducing upstream digital IP packets. The same can also be done forOFDM waveforms as desired.

Once this digital data has been produced, the digital optical fiber nodeor D-CMRTS/DOFN unit will also often have a digital data to opticalconverter device configured to combine any of these digitally encodedupstream RF channel data, upstream digital QAM symbols, and upstreamdigital IP packets and transmit this data, symbols, and packetsdigitally upstream over the optical fiber.

More specifically, note that the D-CMRTS/DOFN units themselves may, insome embodiments, use relatively simple digitization methods, such asRF-analog to optical-digital converters, or QAM demodulators, to extractupstream CATV RF signals, digitize them, and transmit them in a fiberdigital format such as GigE back to the head end (either legacy orimproved). Here again, by simply giving the data packets an appropriatelabel or header, it is relatively simple to aggregate data from manyD-CMRTS units, and send them all back upstream on the same optical fiberchannel (as desired), again both increasing upstream data handingcapability and also saving costs over alternative methods.

Thus in FIG. 6, the large amount of upstream data from neighborhood 1(400, dark dotted parabolas) and the large amount of upstream data fromneighborhood 2 (402, dark dashed parabolas), could in alternativeschemes have originally been sent upstream along optical fiber (222) byD-CMRTS Fiber Node 1 and D-CMRTS Fiber Node 2 (300,304) at variousdifferent optical fiber wavelengths to avoid interference.

However, since, according to the invention the D-CMRTS/DOFN units mayhave either repackaged and remodulated this upstream data into a moreefficient more optical fiber transmission GigE format, this data fromdifferent neighborhoods may instead be sent back using the same opticalfiber wavelength (if this option is desired, which it often may bebecause it is cheaper).

Note that although this disclosure has focused on the all digitaloptical fiber transmission aspects of the invention, and morespecifically on improved virtual head ends that are rendered possible bythis all digital format, this focus should not be intended to excludethe fact that analog optical fiber transmissions may also co-exist alongoptical fiber (222).

Consider the case for neighborhood 3. In some schemes the D-CMTRS unitsor a prior art dumb fiber node (204) may simply and relativelypassively, have transuded the upstream CATV RF waveforms from RF tooptical signals such as infrared optical signals, and then retransmittedthe upstream data otherwise modulated “as is”.

Although this option is not excluded, in a preferred embodiment, thedumb optical fiber node (204) may either be replaced by a dumb digitalconverter optical fiber node that does little more than digitize theupstream CATV RF signal (e.g. using a module such as 601 or 605), andtransmit this digital data upstream on optical fiber (222) according tostandard optical fiber digital formats. As yet another embodiment, theprior art dumb optical fiber node (204) may be retained, but a digitalnode converter unit (401) may be put in place to convert optical fibersignals back and forth between a digital optical format and a legacyanalog format for the legacy dumb optical fiber node (204). Here, thisnode converter unit (401) may, in some embodiments, essentially do thesame type of data repackaging and remodulation functions of previousswitch (220) previously discussed in parent provisional application Ser.Nos. 61/385,125 and 61/511,395, the contents of which are incorporatedherein by reference. Alternatively the legacy optical fiber node (204)can remain connected to the head end by another legacy optical fiber(403) path, and the head end (202), which retains its legacycapabilities, will be able to adequately serve remaining legacy opticalfiber nodes (204) during the upgrade process.

In the present disclosure, switch (220) is instead operating as a multiport digital data switch (220D), which may operate at either onewavelength or a plurality of wavelengths as desired, and the dataextraction, digitization or reconstitution functions, and analog formatto digital data packet repacking functions may instead be moved to otherdevices such as converters (399) and (401).

For example, in this scheme, the upstream data from neighborhood 1 (darkdotted parabolas) and the upstream data from neighborhood 2 (dark dashedparabolas) has been digitized and repackaged by the D-CMRTS/DOFN units(200) into various digital data packets.

Without such digital conversion, the two upstream data sources may havebeen originally sent by the various D-CMRTS/DOFN units on differentoptical wavelengths. But because the data has now been repackaged at theD-CMRTS/DOFN units, now the data from both neighborhoods can be carriedupstream on optical fiber digital data streams (308) and (312) at thesame wavelength along optical fiber (301).

FIG. 7 shows a more detailed view of how the D-CMRTS fiber nodes(300,304), converters (399) and improved digital cable modem terminationsystems (D-CMTS) (500) at a legacy cable head (202), supplemented withimproved D-CMTS line cards, may operate.

For simplicity, again primarily the downstream portion of the system isshown. Generally the D-CMRTS/DOFN units will have an onboard digitaldata switch (560) (operating either with optical fiber digital datapackets, the electrical version of these optical fiber digital datapackets) used to direct various optical fiber data packets to and fromtheir correct destination devices (e.g. 600, 601, 603, 604, 605, 607)inside the D-CMRTS/DOFN.

Although a capability of operating at multiple optical wavelengths isnot required, in an alternative embodiment where operating with aplurality of optical fiber wavelengths is desired, then the switch (560)may optionally also include optical fiber wavelength splitters, such asone or more Brag filters or other device, to separate out the variouswavelengths. These optical fiber wavelength splitters may optionally bea “smart” or tunable filter that may select different wavelengths undermicroprocessor and software control. The different wavelengths selectedby this splitter may then be sent to various subsystems, such as CMRTSunits (604), which can extract the digital data, repackage it, andgenerate CATV QAM signals and/or other RF signals for the CATV cable.

For backward compatibility, the D-CMRTS/DOFN fiber nodes (300), (304)may also have one or more simple optical-digital to analog RF (O-D/A-RF)(600) converters to convert any digitized legacy downstream opticalfiber data, which may contain analog to digital sampled versions ofvarious CATV NTSC, FM, QPSK, or even QAM waveforms back from digitaldata packets to their respective analog RF waveforms again. Depending onthe embodiment, (O-D/A-RF) converters may work directly on downstreamoptical data, or alternatively work on electrical equivalents of thedownstream optical data signals.

The D-CMRTS/DOFN fiber nodes may additionally contain the reverseupstream versions of these units (601). These upstream units will takeselected upstream RF signals from the CATV cable, such as set top boxQPSK channels or even DOCSIS upstream channels as needed, do an analogto digital conversion, fit into data packets, and optionally eithertransduce into upstream optical data packets, or allow a later stagedevice such as switch (560) to transduce into upstream optical datapackets to send back to the head end.

Also for backward compatibility, the D-CMRTS/DOFN fiber nodes (300),(304) may also have one or more QAM remodulator devices (603) to takedemodulated QAM symbols from the downstream optical data packets, andconvert these back into RF QAM waveforms carrying the same data payload,and then send downstream on the CATV system via RFcombiner/splitter/duplex (606). Again depending on the embodiment, theseQAM remodulator devices may work directly on optical data, oralternatively work on electrical equivalents of the optical datasignals.

These QAM remodulator devices may additionally contain the reverseupstream RF QAM demodulator versions of these units (605). Theseupstream QAM demodulator units may take selected upstream QAM RF signalsfrom the CATV cable, such as various legacy DOCSIS upstream QAM channelsas needed, demodulate the RF QAM waveforms to extract the underlying QAMsymbols that generated the waveforms, fit these demodulated upstream QAMsymbols into data packets, and optionally either transduce these QAMsymbols into upstream QAM symbol optical data packets, or allow a laterstage device such as switch (560) to transduce into upstream QAM symboloptical data packets to send back to the head end.

The D-CMRTS units may additionally contain one or more optical datapackets (e.g. optical IP data packets) to RF QAM waveform converters(607). These IP to QAM converters are useful for, example, convertinglegacy broadcast QAM channels from a legacy head end that have beendemodulated at the legacy head end and packaged into optical datapackets for more compact (e.g. lower bandwidth needed) transport. The IPto QAM converters can also work directly with data coming from theinvention's improved virtual head end (1120) as well. Using eitherapproach, it is possible to transmit more data over the optical fiberthan would be possible than if the entire legacy head end analog QAMchannel waveforms had instead been transposed to equivalent optical QAMwaveforms. In some embodiments (not shown), the D-CMRTS units may alsocontain the reverse version of these units that takes upstream QAM RFdata, demodulates it, repackages the upstream QAM symbols into IP datapackets for optical upstream transmission.

The D-CMRTS/DOFN fiber node (304) may also contain one or more CMRTSunits (604) that may select at least some of the GigE formatted data(310), (310), (307) from the optical fiber (222) QAM modulate this data,and send it to the CATV cable. (226) according to the scheme previouslydiscussed in FIG. 4D. The CMRTS (604) portion of the D-CMRTS unit (304)may in some embodiments generally function as previously discussed incopending application Ser. No. 12/692,582, the contents of which areincorporated herein by reference.

Although again, a key advantage of the system is that at least in theinitial upgrade stages, it can be made almost totally transparent (i.e.capable of running with) legacy HFC software, it should be appreciatedthat to provide additional functionality, particularly when used withthe invention's improved virtual head end, further software upgrades maybe desirable. Here, such an upgraded mix and match system will impose aconsiderable configuration and management problem on the D-CMTS units atthe cable head (202). As previously this complexity may be handled by acomputerized network management system and software termed the “virtualshelf”.

In one embodiment of the improved “virtual shelf” system, suitable forworking with upgraded legacy head ends, the D-CMTS shelf and improvedD-CMTS line cards may optionally be configured with both packetprocessors (610), and MAC (612) and PHY (614) devices or functionalityto transmit standard CATV analog, QAM, NTSC, QPSK, and DOCSIS analogsignals, where the signals may be digitized by converter (399) andtransported over the optical fiber as a series of legacy optical IP datapackets (307).

Although according to the present invention, the virtual shelf softwareis now incorporated as part of the virtual CCAP control software (1102),used to control edge router (1104), much of the underlying logic issimilar to that used for the upgraded legacy head end discussed in FIG.7.

Returning to how the virtual shelf software can be used to controlupgraded legacy virtual shelf systems, the same CMTS shelf and linecards may also be configured with packet processors (616), MAC (618) andPHY (620) functionality to some or all of this data as GigE formatteddata as various digital optical IP data streams (e.g. 308, 310, 312) onone or optical fiber wavelengths.

As a result, the MAC (618) and PHY (620) for (308, 310, 312) can bedifferent from the MAC (612) and PHY (614) used for the optical fiber IPdata packets for the legacy signals (307).

The exact mix of signals transmitted and received by the improved linecard will vary depending upon what sort of fiber nodes are connecteddownstream (southern end) to the line card.

For example, if all of the fiber nodes were “dumb” prior art fiber nodes(204), then the D-CMTS line card may only transmit legacy digitizedoptical IP data packets (307), and after passing through converter (399)the functionality of that particular D-CMTS line card could be backwardcompatible with prior art CATV DOCSIS equipment and fiber nodes.

That is, the optical fiber legacy IP data stream (307) could transmitthe full set of DOCSIS channels, simply by brute force analog todigital, digital optical transmission, and digital to analog conversion;and/or brute force QAM demodulation into QAM symbols, digital opticaltransmission, and QAM symbol remodulation back into QAM waveformmethods.

By contrast, if all of the fiber nodes were “smart” improvedD-CMRTS/DOFN fiber nodes (300,304), then the improved head end D-CMTSand CMRTS line card might elect to maximize all or nearly all data tothe various households by skipping legacy mode, just sending all datavia the non legacy optical IP data packets (308, 310, 312) one or morewavelengths in an optical digital transport protocol such as GigEformat, and leave it to the D-CMRTS units (300), (304) to then handlethe reformatting and conversion to CATV RF modulation schemes such asQAM modulation.

This scheme would thus allow the highest amount of customized data to besent to the houses on that particular stretch of cable.

Again in the legacy head end context, in a mixed mode HFC system using amix of “dumb” fiber nodes (204) and “smart” CMRTS fiber nodes (300,304)(as previously shown in FIG. 5), the improved D-CMTS and D-CMTS linecards could ideally elect to operate in both legacy and GigE modes, thustransmitting and receiving standard video channels (114) and DOCSIS(116) information to and from neighborhood 3 (served by the “dumb” fibernode), using the digital converter (399), optical node converter (401),and the legacy optical fiber digital IP packet data stream (307) tocontinue giving adequate service to neighborhood 3.

As previously discussed, in order to manage this complexity, thefunctionality of the improved head end D-CMTS and D-CMTS line cards, aswell as usually the functionality of the D-CMRTS fiber nodes (300,304),may be extended by use of additional “virtual shelf” network managementcomputers, controllers, and software, here assumed to be now part ofvirtual CCAP controller (1102).

In one embodiment, a unified network management system (exemplified by,for example, the ConfD management system provided by Tail-fincorporated) is added to the improved D-CMTS and line card (now virtualCCAP controller 1102) to unify the network and D-CMTS hardware andvirtualization layer, provide operating system services, managemiddleware, and configure the system to use the proper networkingprotocols. In this embodiment, all or at least much networkconfiguration data is stored on a database in the D-CMTS manager, andthe configuration of the network is controlled by a process in which themanagement software (ConfD) communicates over IPC (sockets) with appsthat control the function of various packet processors, MAC, and PHYdevices on the improved D-CMTS and D-CMRTS/DOFN units. According to theinvention's virtual head end concepts, the main difference may be thatthe head end commands will be generally directed to the operation of theedge router (1104), while the commands for the DOFN commands will berelayed (often through edge router 1104) to the various remote DOFN inthe field.

Here the computer or processor and associated software memory (622) areshown directly controlling the operation of an improved D-CMTS unit byway of various other controllers (624), (626) located in the improvedD-CMTS backbone and line cards (500). The communications between this“virtual shelf manager” (622) and the local controller processors (624),(626) are shown as dashed lines (628). The virtual shelf manager mayalso control the operation of a level 2/3 switch (629) and/or otherdevices that connect the improved D-CMTS unit to the media content(210), IP backbone “cloud” (212), and other services provided by thecable head (202). The operation of the virtual CCAP controller softwarecan generally be the digital version of this teaching.

The virtual CCAP software/virtual shelf manager may often also managethe configuration of the various “smart” D-CMRTS/DOFN fiber nodes(300,304), often by communicating with controllers and applicationssoftware embedded with the D-CMRTS/DOFN fiber nodes (not shown). Giventhe typically long distances between the D-CMRTS/DOFN fiber nodes(300,304) and the virtual shelf manager (622) and improved D-CMRT (500)(which will often be located at the cable head, miles or more away fromthe various nodes (300,304)), the D-CMRTS/DOFN fiber node (300,304) tovirtual shelf manager (622) communication will often be done by varioussignals and signal protocols communicated by the optical fiber orfibers. In one preferred embodiment, socket based inter-processcommunication (IPC) protocols are used.

This enables the configuration of the D-CMTS shelf, and indeed theoverall network, to be rapidly reconfigured to meet the ever changingnetwork model generated by the invention. Often it will be convenient tostore this network configuration, as well as the properties of thevarious network devices, in a configuration database (630) andconfiguration database memory device (not shown). Again the operation ofthe virtual CCAP software may be similar.

FIG. 8 shows more details of the Cable Modem Remote Termination SystemCMRTS (604) portion of the D-CMRTS/DOFN fiber node. At a higher or atleast alternate level of abstraction, at least the CMRTS portion of theD-CMRTS/DOFN fiber node, and often the entire circuitry in the DOFNdevice may typically comprise at least a first set of QAM-RF packetprocessors (700) with MAC and PHY units that select the desired opticalIP downstream data from the GigE formatted data, and convert thedownstream optical IP packet data to a plurality of radiofrequency (RF)QAM waveforms (channels) and output this data downstream (702) to thelocal CATV cable.

This CMRTS unit (604) may also optionally comprise a second set ofRF-upstream packet processors (704) that will read the upstream RFsignals (data) sent by cable modems connected to the local CATV cable(706). Note that these packet processors (704) may contain MAC and PHYunits that are capable of recognizing the upstream data. Thus if theupstream data is sent using an unusually wide upstream bandwidthaccording to scheme (390), the MAC and PHY units will recognize it. Theunits will then convert this upstream data to appropriate optical IPEthernet data packets, or other digital optical data communicationsprotocols suitable for communicating this cable modem data back upstreamto the improved D-CMTS (500) at the cable head.

The operation the DOFN, as well as both packet processors (700), (704)as well as other devices such as O-D/A-RF or RF-A/D-O converters (600),(601), QAM remodulators and demodulators (603), (605), CMRTS unit (604)and the like may be remotely controlled by the virtual shelf manager(622) by way of suitable controllers (often microprocessors), and localapplications software (Apps) that intercept data from the optical fiber(222) and receive and send commands, often by way of a specializedcommunications protocol such as the previously discussed socketsprotocol. Again the operation of the virtual CCAP control software maybe similar.

At a deeper level that exposes more details of the PHY units in both theQAM-RF packet processor (700) and the optional RF-upstream packetprocessor (704), The DOFN's CMRTS unit (604) will normally comprise MACand PHY units, and a data switch (710), at least one controller (often amicroprocessor and associated software, not shown), various QAMmodulators (712) to take the GigE data and convert, QAM modulate, andfrequency shift the data as needed to fit the limited CATV RF bandwidth.To do this, DOFN's CMRTS unit may employ a controllable clock generator(714) to control the frequency and timing of the QAM channels, as wellas variable gain amplifier (VGA) units (716), (718) to help the PHYportions of the units manage the analog processes in converting signalsback and forth between the CMRTS/DOFN unit (300,304) and the cable RFsignals.

Various network timing protocols may be used to synchronize the varioushead end units, DOFN and other HFC network components. In someembodiments, it may be useful to employ the IEEE-1588™ standard tosynchronize the various network real time clocks, however otherprotocols, such as the Network Time Protocol, RFC 1305 (NTP), Satellitebased Global Positioning System (GPS), TTP, and SERCOS (IEC 61491) mayalso be used.

As before, the MAC and PHY units and the data switch (710) switches, andthe switches that control the QAM modulators (712) and analog to digital(A/D) units (720) may be remotely controlled by the virtual shelfmanager (622) by local (embedded) controllers (often microprocessors)and associated applications software by commands to and from the VirtualShelf software. As before, often these commands may be sent over thesame optical fiber pathways normally used to transmit other data, andagain may use socket based inter-process communication (IPC) protocols.Again the operation of the virtual CCAP control software may be similar.

As before, for backward compatibility, the return process for processingupstream data can optionally implement the RF-A/D-O converters (601)and/or QAM demodulators (605) digitize and send the upstream signalsback with essentially no modification other than digitization, datapacket conversion, and optical conversion process.

Generally, the upstream data will be detected by whatever equipment isbest suited to interpret the invention's various upstream datamodulation methods—e.g. suitable equipment to intercept and decode thewider bandwidth upstream data and the like.

In this scheme, for simplicity, it is assumed that these methods will beimplemented by high speed DSP or software controlled receiver that canamplify the various signals, digitize them, and then decode according tothe appropriate algorithms, but of course other methods may also beused. Other hardware, such as ASICs, FPGA, DSP, and the like may also beused, as per U.S. patent application Ser. No. 13/555,170, the contentsof which are incorporated herein by reference.

In one embodiment, variable gain amplifier (VGA) units (718) willconvert the incoming upstream RF signal from the local neighborhood CATVcable into a signal which is then digitized by the A/D converter andclock generator, analyzed and repackaged by the MAC and PHY units (710)into a GigE or other optical fiber optimized signal, and then sentupstream along the optical fiber through various optical fibersplitter/combiner units (710). This process may be controlled bycommands from the Virtual Shelf software.

FIG. 9 shows more details of how the virtual shelf manager (622) and theconfiguration database (630) (previously shown in FIG. 7) may controlthe functionality of most or all of the plurality of D-CMRTS/DOFN fibernodes (300,304), improved D-CMTS (500) D-CMTS line cards (502), andoptionally other active nodes and switches in the HFC network system.Again the operation of the virtual CCAP software may be similar.

In this example, the virtual shelf manager software (622) is shownrunning as a module of a broader D-CMTS manager software package (800);however it also may be run as a standalone package. The D-CMTS managersoftware (800), which will often be run on one or more computerprocessors which may be located at the cable head (such as at controller(1102) when the improved virtual head end 1120 is used) or otherconvenient location, will often be based on network configurationmanagement software (802). Such network configuration software (802)(also called the Operational Support Systems (OSS) software) may be, forexample, software based upon the ConfD network management softwareproduced by Tail-f Systems Corporation, Stockholm Sweden (Internationallocation) and Round Hill Va. (US location).

In this embodiment, use of software such as ConfD is useful because thistype of network management software also provides a number of convenientand commonly used interfaces to allow users to interact with the networkand control then network configuration. These interfaces may includeNETCONF management agents, SNMP agents, Command Line Interfaces (CLI),Internet (Web) interfaces, and other agents/interfaces as desired.

The virtual CMTS shelf software might previously have been used tocontrol the status of the various D-CMTS line cards (500) (and now usedto control virtual head end 1120) and the D-CMRTS/DOFN fiber nodes(300,304) will often interact with a network configuration database(630) run under the control of this network configuration software(802). The virtual D-CMTS shelf software will in turn send commands outto most or all of the various remote D-CMRTS/DOFN fiber nodes, as wellas control virtual head end operations analogous to the operation of theD-CMTS (500) at the cable head, and other devices as desired. Aspreviously discussed, one preferred way for this control to be achievedis by way of socket based inter-process communication (IPC) protocolsand packets (804), which may be sent over the same optical fiber linesused to send the other data. In this situation, for example, controllersrunning various types of application software (Apps) in the plurality ofremote packet processors (700), (704) in the remote D-CMRTS fiber nodes(300,304) can listen for appropriate commands from the virtual CCAPcontrol software/virtual shelf manager (622), and adjust the operationof the D-CMRTS packet (700), (704) processors accordingly. These D-CMRTSfiber nodes can also transmit their status back to the virtual shelfmanager using the same protocols.

The device configuration database (630) of the virtual CCAPsoftware/virtual shelf manager system will often have multiple datafields, including fields that contain the identification code and/oraddresses of the various D-CMRTS units in the network (D-CMRTSidentifier fields). The database will also usually have information onthe status of the various cable modems connected to the various D-CMRTSunits, including the cable modem identification data (cable modemidentification data fields) and the privileges of the various users thatare associated these various cable modems. For example, one user mayhave privileges to access a broad array of services high bandwidthupload and download data, while another user may have limited access toa different set of services and more limited upload and download dataprivileges. Other functions that may be implemented include eventlogging, Authentication, Authorization and Accounting (AAA) support, anextended version of a DOCSIS Management Information BASE (MIBs)functions, etc.

Other fields that normally will be in the database will includeinformation as to user identification fields (user privilege fields),available extended DOCSIS channels, available IP addresses, instructionsfor how to remotely configure the various D-CMRTS software controllableswitches, and instructions for how to remotely configure the variousD-CMRTS/DOFN software controllable RF packet processors.

The virtual CCAP software, such as the virtual shelf manager andconfiguration database, as well as other components of the system, willusually be run on a computer system (e.g. controller 1102) with at leastone microprocessor, as well as access to an edge router (1104) thatreplaces the standard hardware and software, such as MAC and PHY units,that will enable the virtual shelf manager to send and receive datapackets (often through the IPC protocol) to the various remoteD-CMRTS/DOFN units on the network.

The OSS software (802) can inform the virtual CCAP software/virtualshelf manager software about the privileges, certificates, andencryption keys assigned to the various users. The OSS can also setpolicies or allocation limits regarding the frequency and bandwidth thatwill be assigned to the various channels. The OSS can also respond toqueries from the virtual shelf manager when new modems are detected. TheOSS can further take statistical data collected by the virtual shelfmanager, such as packets transmitted and received, volume of data, anduse this information for billing and network management purposes.

Further information on OSS functions, and more examples of functionsthat may be implemented in the OSS software for the invention, may befound in Misra, “OSS for Telecom Networks: An Introduction to NetworkManagement”, Springer (2004).

For example how this system would operate, consider the case where a newcable modem is first connected to the system. The cable modem may sendan upstream signal (226) to the D-CMRTS (604). The RF-up packetprocessor (704) in the DCMRTS (604) will in turn collect the informationrelating to the cable modem identification number, and other relevantparameters, repackage the data in a digital format, and send it backupstream to the virtual shelf manager system on the fiber GigE link(302) or, in the improved version, to the virtual CCAP controller andsoftware (1102).

As did the virtual shelf manager system (622) previously, the virtualCCAP controller and software (1102) will look up the cable modemidentification data in the device configuration database (630), anddetermine the privileges of the user associated with the cable modemidentification data, and depending upon the value of the user privilegefield, available extended DOCSIS channels, and available IP addresses,send data packets (often via edge router 1104) to the D-CMRTS (700)unit, often by way of the IPC protocol (804) that controls thatparticular cable modem. The virtual shelf manager may also control thefunction of any household gateway devices.

These data packets will interact with applications (e.g. App 1, App n)and configure the software controllable switch(s) on the D-CMRTS unit(700), to configure the software controllable switches on the QAM-RFpacket processor (700) and the cable modem available IP addresses orTDD-FDD gateway addresses so as transmit downstream data to the cablemodem on a first available DOCSIS channel. The data packets will alsoconfigure the software controllable RF packet processor (704) to receiveupstream data from the cable modem on a second available DOCSIS upstreamchannel and IP address and retransmit the upstream data as a thirdupstream digital optical fiber signal (302).

Often the virtual CCAP control software (1102) virtual shelf manager(622) will handle IP addresses for the cable modems and optional gatewaydevices through the proxy Dynamic Host Configuration Protocol (DHCP)service, or other method.

Alternative types of residential gateways capable of allowing householdCATV equipment that is designed for the standard DOCSIS CATV protocolsthat call for the 5-42 MHz range of upstream frequencies to work withCATV cables an extended range of upstream frequencies are also possible.This gateway equipment will be designed to “fool” the household CATVequipment into thinking that it is connected to a standard CATV cablethat is capable of carrying standard 5-42 MHz upstream data, but thatthis standard CATV cable is relatively uncongested—that is that acomparatively large portion of the 5-42 MHz spectrum is free for use. Infact, the gateway equipment may then either shift the frequency of thehousehold 5-42 MHz upstream data (e.g. QAM channels) to an alternatefrequency (e.g. convert a 20 MHz upstream QAM channel to, for example, a100 MHz QAM channel) for transmission over the CATV cable, oralternatively convert the upstream QAM channel(s) into spread spectrumsignals. In either event, the converted upstream signals will then besent upstream on the CATV cable to the D-CMRTS optical fiber node, orother fiber node as appropriate. This data may then be converted tooptical fiber data and sent on to the cable head as appropriate.

Adaptive cancellation methods, useful for such adjustableupstream/downstream frequency ranges were taught in copendingapplication Ser. No. 13/400,415 “METHODS OF ADAPTIVE CANCELLING ANDSECONDARY COMMUNICATIONS CHANNELS FOR EXTENDED CAPABILITY HFC CABLESYSTEMS”, the contents of which are incorporated herein by reference.

FIG. 10 shows an alternate type of residential gateway (1100) that canconvert between a CATV cable system with an extended frequency allocatedfor upstream data (e.g. 5-547 MHz or alternative upstream range offrequencies), and residential equipment designed for the standard 5-42MHz range of upstream frequencies.

Here CATV cable 226 is carrying extended range frequency upstream data(390), which may have far more upstream MHz bandwidth than the standardlimited CATV 5-42 MHz upstream bandwidth. However the problem is thatwithin the household, the CATV equipment—e.g. set top boxes, cablemodems, may be legacy CATV equipment that only is capable of sendingupstream data on the standard 5-42 MHz bandwidth. In this example, thegateway (1100) serving the house may be an extended FDD upstream gatewaythat contains the equipment necessary to frequency shift the householdCATV equipment upstream signals to alternate frequencies forretransmission on the CATV cable (226). Thus, for example, the upstreamdata capability of a neighborhood could be extended about 10× byreallocating and transmitting the normal 5-42 MHz upstream data in abroader 5-547 MHz range, and tricking every household into thinking thatit had free access to a 5-42 MHz upstream range of frequencies that wasonly 1/10 as congested as it was before.

As previously discussed, alternate types of gateways are also possible.Such alternative methods were discussed in application Ser. No.13/555,170, which was a CIP of application Ser. No. 13/035,993 “METHODOF CATV CABLE SAME-FREQUENCY TIME DIVISION DUPLEX DATA TRANSMISSION”,now U.S. Pat. No. 8,365,237, the contents of these applications areincorporated herein by reference.

Other alternative embodiments of the invention are also possible. Inthese alternative embodiments, the CMRTS or D-CMRTS/DOFN units can havemultiple outputs, such as multiple CATV cable outputs, or even a mix ofCATV or Coax cable outputs and, other output types such as data outputs(e.g. GigE or other data output), telephony outputs, and the like.

The present invention may also be used for alternative HFCconfigurations, such as copending application Ser. No. 13/346,709 “HFCCABLE SYSTEM WITH WIDEBAND COMMUNICATIONS PATHWAY AND COAX DOMAINNODES”, and Ser. No. 12/907,970 “HFC CABLE SYSTEM WITH SHADOW FIBER ANDCOAX FIBER TERMINALS”, the contents of which are incorporated herein byreference.

In one alternative HFC configuration, discussed in more detail herein,the DOFN concept may be further extended in a manner that allows forgreatly simplified, yet highly powerful, systems and methods for HFCsystem management. In particular, in addition to all digital over fiberdata transmission, with good legacy RF capability on the cable portionof the HFC system, in some embodiments of the invention, the HFC headend can be simplified to the point where it can now become a “virtualhead end”, with greatly reduced power requirements and spacerequirements.

In the following discussion, the “Gainspeed EtherNodes” may be viewed asbeing a set, subset, or superset of the previously described DOFNdevices and methods.

Much of the following discussion will focus on edge routers. Edgerouters are defined by techopedia as: “An edge router is a specializedrouter residing at the edge or boundary of a network. This routerensures the connectivity of its network with external networks, a widearea network or the Internet.” Because they straddle the boundarybetween different networks, Edge routers often operate using the BorderGateway Protocol (BGP) protocols as a standardized exterior gatewayprotocol to exchange routing and reachability information between thedifferent autonomous systems. Thus one important invention insight isthat, once the HFC CATV system has been converted to all digitaloperation using the methods described previously in this disclosure,with suitable control methods, the rather cumbersome HFC CATV systemprior art head end (202) (Cable head) can now be replaced with moreefficient edge router technology.

In this disclosure a specific type of edge router, namely the Juniper MXSeries 3D Universal Edge Routers, will be used as a specific example ofthe type of edge router devices that may be useful to implement theinvention. However it should be understood that this specific example isnot intended to be limiting, and other types of edge routers may also beused.

As described by Juniper Networks, the MX series of 3D Universal EdgeRouters are described in various documents including NETWORK SCALINGWITH BGP LABELED UNICAST Design and Configuration Guide, 8020013-001-ENJanuary 2010, and “Universal Edge Service Innovations Propelling ServiceProvider Growth Universal Edge Revolutionized with Application ServiceCapabilities, Network and Service Virtualization, and ProgrammablePlatform, the contents of both of which are incorporated herein byreference.

FIG. 11 shows an overview of the virtual converged cable access platform(e.g. virtual CCAP, virtual cable head). Here the MX device (1104) maybe an edge router such as the Juniper Networks MX series of 3D UniversalEdge Routers, and the Gainspeed EtherNodes (1106) may be devices such asthe digital optical fiber nodes (DOFN) devices (300,304) previouslydescribed herein.

Because, as will be discussed, much of the control aspects of theinvention's CATV head end can be controlled by the controller (1102)software, at least some of which can be stored on remote servers, andbecause much of the CATV data content can also be stored on remoteservers, in some embodiments, the invention's virtual head end can beviewed as providing the CATV cable network with a “cloud based headend”.

Here a controller device (1102) (e.g. Gainspeed Controller, also termeda “controller”, (1102) and a virtual CCAP controller) can interface withsome or all legacy or next generation cable operator servers/systemssuch as SNMP, IPDR, PCCM, NETCONF, CLI and so on. This controller canthen control the end-to-end process of getting the various cable modem(CM) and Customer Premises Equipment (CPE devices) online to the system.This can implement the functions such as Dynamic Host ConfigurationProtocol (DHCP) relay, edge router interfaces (e.g. the Juniper NetworksMX edge router programmatic interface) and so on.

The edge router (1104) (Juniper Networks MX device) can handle some orall Level 3 and 3+ control and data plane functions. This can includeIP/MPLS control plane (e.g. LDP, PGP, ISIS, OSPF functions and so on).The edge router can also handle Level 3 processing (such as IP/MPLSforwarding, Subscriber QoS, Packet Filters, VLAN manipulation, and soon). The digital optical fiber nodes (DOFN, also called the GainspeedEtherNodes) can handle all Cable radio frequency (RF) and DOCSISfunctions. This can include modulation, MAC/PHY, SF, QoS, Encryption,Scheduling, and so on.

FIG. 11 shows an example of a radically redesigned, and at the same timegreatly size and resource reduced, “virtual head end” (1120) formed fromthe combination of a virtual CCAP controller (1102), and an edge router(1104) that, when combined with the inventions DOFN nodes, can be usedto greatly simplify the power utilization, space, and cost requirementsof legacy head ends (202).

In FIG. 11, HFC data (video, audio, internet data, and the like) isshown as being delivered from various operator servers (1100). Theseoperator servers in effect provide the previously described mediacontent data (210) and IP backbone data (212). In this figure, isfurther convenient to consider any converter operation (399) to also bedone at the operator server level (1100).

Thus these operator servers (1100), such as the cable operator serverssend and receive data, often by an optical fiber connection (222), toand from the virtual head end (1120), also sometimes referred to as a“hub”. As previously discussed, this virtual head end section in turnwill often contain one or more Virtual CCAP controllers (1102) (called a“Gainspeed controller in this example), and one or more edge routers(1104). These edge routers may in some embodiments incorporate thefunctionality exemplified by the Juniper Networks “MX” edge router.

Here the Gainspeed Controller (1102) instantiates the Virtual CCAP. Inparticular, it interfaces with some or all existing cable operatorserver/systems, such as SNMP, IPDR, PCMM, NETCONF, CLI, and othersystems. The unit also orchestrates the end-to-end process of gettingthe cable modem (CM) and Customer Premises Equipment (CPE) devicesonline. In some embodiments, this can also implement DHCP relay, as wellas company proprietary functions such as the JNPR (Juniper) MXProgrammatic interfaces, and so on.

Put alternatively, Virtual CCAP controller (1102) handles much of thelogic of the previously discussed CMTS manager (800), and may forexample, implement the logic for the subscriber manager, virtual shelfmanager (622), network configuration management software (802), andconfiguration database (630) previously discussed in FIG. 9 andelsewhere. In essence the Virtual CCAP is the “brains” of the virtualhead end, and is implemented mostly in software, while the edge routeris the “brawn” (data packet switching capability) of the virtual headend, and does the massive amount of data packet transfer needed tosupport the HFC CATV system.

The software for the Virtual CCAP controller/Gainspeed controller (1102)can reside anywhere. Although to minimize latency, some of the more timesensitive portions of the software may reside on the physical controllerhardware (1102) itself (which will generally comprise at least onecomputer processor, and more typically large numbers of computerprocessors, some of which may be specially configured for the task), atleast the less time sensitive portions of the Virtual CCAP controllersoftware can reside elsewhere, and may even be located on remoteservers, also called “the cloud”, or at least be controlled remotely.

Note also that the process of transforming a legacy HFC system with alegacy head end and legacy optical fiber nodes can be almost completelytransparent to the end users in the various households, and the cablemodems (208) and other consumer premises equipment (CPE) do not need tobe changed during the transition. Here for example, in a first step,legacy optical fiber nodes (204) can be swapped with DOFN (300,304), andthese DOFN operated using legacy head ends/cable heads (202) andconverters (399), and the household service and legacy cable modems willcontinue to operate. Then, when convenient, the legacy head end (202)and converter (399) can be swapped out for the invention's virtual headend (1120). The various legacy household cable modems (208) and otherlegacy equipment (e.g. televisions and the like) can continue tooperate. Thus the cable operator can gracefully upgrade the capabilitiesof the HFC system without breaking a lot of subscriber equipment.Eventually, of course, to provide improved service, the legacy cablemodems and other household equipment may also be upgraded, but this canbe done gradually, and without distress to the large number of cablesubscribers.

The Juniper MX or other type edge router (1104) can be used to handlesome or all Level 3 (L3+) control and data plane functions, such asthose previously described in FIG. 7 (629), (624), (616), (610) and thelike. This can include IP/MPLS control plane functions such as LDP, BGP,ISIS, OSPF, and so on. This can also include Level 3 packet processing,such as IP/MPLS forwarding, Subscriber QoS, Packet filters, VLANmanipulation, and so on.

Thus to reiterate, the combination of the Gainspeed controller (1102)and edge router (1104) can be used to create a “virtual head end” that,in combination with the invention's DOFN, can convert a legacy cablesystem to all-digital operation, as well as replace the high power andhigh space requirements of legacy head ends with a lower power lowerspace requiring “virtual head end”. This “virtual head end” can replacelegacy cable head (head ends) such as legacy cable head (202) shown inFIG. 5, or more specifically the combination of the Cable head (202) andthe converter (399) shown in FIGS. 5 and 6.

With respect to the “operator servers” (1100), in some embodiments,these operator servers can act to replace the media content servers orstorage, such as media content (210) as shown in FIG. 6. Because,according to the invention, even legacy signals, such as legacy QAMchannels are transmitted in all digital formats, in some embodiments, itmay be convenient to pre-digitize or pre-sample various channelsintended to be reconstituted into legacy RF waveforms at the DOFN, andstore this media in a pre-digitized legacy format. This can help reducethe amount of subsequent processing that the Gainspeed controller (1102)and edge router (1104) will need to do in order to transmit digitizedlegacy signals to the various DOFN/Gainspeed EtherNodes (1106)

The Gainspeed Ethernode(s) (1106) can handle some or all RF and DOCSISfunctions. This can include modulation, MAC/PHY, SF QoS, Encryption,Scheduling, and so on.

In this embodiment, the CATV cable network can be viewed as havingalmost a “cloud based head end” or “virtual head end”. Here a controllerdevice (e.g. Gainspeed Controller) can interface with some or all legacyor next generation cable operator servers/systems such as SNMP, IPDR,PCCM, NETCONF, CLI and so on. This controller can then control theend-to-end process of getting the various cable modem (CM) and CustomerPremises Equipment (CPE devices) online to the system. This canimplement the functions such as DHCP relay, edge router interfaces (e.g.the Juniper Networks MX edge router programmatic interface) and so on.

The controller device, alternatively called the Virtual CCAP controller,will generally consist of at least one processor, and virtual CCAPcontroller software. This virtual CCAP software can assume some or allof the functionality previously discussed in FIG. 9. In someembodiments. the virtual CCAP software can be configured to run on thevirtual CCAP controller's at least one processor, and to issue commandsto said edge router. Some commands may instruct the edge router tointerface with legacy operator servers or systems using variousprotocols, such as the simple network management protocol (SNMP),internet protocol detail record (IPDR), packet cable multimedia (PCMM),Network Configuration Protocol (NETCONF), command line interface (CLI)protocol, or other protocols. Other commands may instruct the edgerouter to manage the process of bringing cable modem and customerpremises equipment online to the HFC cable network, and to furtherimplement dynamic host configuration (DHCP) relay and edge routerprogram interface protocols. Examples of some of these edge routercommands, and edge router responses back to the controller, can be seenin more detail in FIGS. 12-15.

The edge router (Juniper Networks MX device) can handle some or allLevel 3 and 3+ control and data plane functions. This can includeIP/MPLS control plane (e.g. LDP, PGP, ISIS, OSPF functions and so on).The edge router can also handle Level 3 processing) such as IP/MPLSforwarding, Subscriber QoS, Packet Filters, VLAN manipulation, and soon). The digital optical fiber nodes (DOFN, also called the GainspeedEtherNodes) can handle all Cable radio frequency (RF) and DOCSISfunctions. This can include modulation, MAC/PHY, SF, QoS, Encryption,Scheduling, and so on.

In some respects, the functionality of the Gainspeed controllers, aswell as other elements of the system can best be exemplified by FIGS.12-15.

The hub section (virtual head end 1120) will in turn often communicateby optical fibers to one or more Gainspeed EtherNodes. The GainspeedEtherNodes in some embodiments may have a structure and function to thepreviously described Digital Optical Fiber Nodes (DOFN). In particular,these Gainspeed EtherNodes will often connect to both optical fibers, aswell as to the CATV coax cable. Thus the Gainspeed EtherNodes will oftenhave both optical input and output (from the optical fibers) as well asRF input and output to the CATV Coax cable.

FIG. 11A shows some of the similarities between the previously discussedDOFN and the Gainspeed EtherNodes (1106). FIG. 11A is based onpreviously discussed FIG. 4C, and shows how the various functions of thecable head end can be handled by the present invention's virtualconverged cable access platform (show in FIG. 11, and also in thefollowing figures), while the previously discussed Digital Optical FiberNodes (now referred to in the alternative as the Gainspeed EtherNodes)continue to handle the interface between the cable RF signals, and theoptical fiber data.

Note, however that there can be some exceptions to the rule that theGainspeed EtherNode will generally have an optical input and output. Insome cases, for example when it is physically difficult to route opticalfiber to a particular node, the Gainspeed EtherNode may instead transmitdata that might normally have gone over the optical fiber over the coaxcable at very high frequencies, such as the 1 Gigahertz plus (1 GHz+)frequencies. Here the methods of copending and parent application Ser.No. 13/964,394 “HFC CABLE SYSTEM WITH ALTERNATIVE WIDEBANDCOMMUNICATIONS PATHWAYS AND COAX DOMAIN AMPLIFIER-REPEATERS” may beused. The complete contents of U.S. patent application Ser. No.13/964,394 are incorporated herein by reference.

The CATV coax cable in turn, at the cable plant, will then connect tovarious households. Each household may have various devices such ascable modems (CM) and Customer process equipment (CPE).

In some embodiments, all signals transmitted over the optical fiber willbe digital signals. The Gainspeed EtherNodes/DOFN may be configured totransform or convert at least some of these digital signals to legacy RFCATV signals as desired. Thus in some embodiments, the present inventioncan deliver and receive backward compatible RF signals to legacyhousehold cable modems, television, CPE and other devices.

One important aspect of the invention is that it maps DOCSISfunctionality into edge router functionality. The mapping is across thedifferent elements, devices, or modules of the system. Putalternatively, one important aspect of the invention is that itvirtualizes DOCSIS across the edge router.

As shown in FIGS. 12-15, the invention can orchestrate the end to endprocess of getting various cable modem and customer process equipment(CPE) devices online, including legacy CATV cable modems and CPE.Indeed, one important aspect of the invention that it enables the cableoperator to set up a service that goes to households, and can utilizeexisting CATV coax cable and existing cable modems and CPE devices tomaintain backward compatibility where desired.

In some embodiments, the invention can implement the various levels offunctionality needed to get legacy cable modems online, and (forexample) to allow household computers to connect to the internet.Additionally, the invention can also be configured to provide variouscustomer levels of service. That is, it can be configured so thatcustomers that pay for a first level of service can obtain a first levelof bandwidth (i.e. data carrying capability), customers that pay for asecond level of service can obtain a second level of bandwidth, and soon.

In other embodiments, the invention may also allow the cable operator todeliver various different types and levels of service according tovarious customer specific service contracts

According to the invention, the Gainspeed EtherNodes/DOFN can beconfigured to implement or provide CMTS (Cable Modem Termination System)and Layer 2 access. Because these Gainspeed EtherNodes/DOFN are right ofthe edge of the CATV coax cable plant, this layer is called the “outsideplant”, to distinguish from the various coaxial cable devices in the“inside cable plant”.

Thus according to the invention, the Gainspeed EtherNodes/DOFN in the“outside plant” are managing all of the cable modem access over thecoax. These Gainspeed EtherNodes/DOFN essentially forward traffic fromthe network and from the edge router to the various coax cablehouseholds and neighborhoods in the coax plant, and vice versa (e.g.from the cable plant all the way to the edge router).

The invention's systems and methods can also be configured to handlecoordination. Depending upon service levels, the system can beconfigured to allow one customer cable modem to receive and transmitmore data than a different customer's cable modem. The invention canalso be configured to prioritize traffic, reshape traffic, and also dofull content inspection as desired.

Depending upon the configuration setting, some of the above processesmay be done at the Gainspeed EtherNode/DOFN, and some may get done atthe edge router (1104) as assisted by controller (1102). Here systemresources can play an important role in determining what parts of thesystem handle what processes. Often, for example, the operator may findit preferable to assign the task of packet reshaping to the edge router,because typically edge routers will have more onboard intelligence andmore system resources to accomplish this task.

Another system device, here called the Gainspeed controller or virtualCCAP controller (1102), can be used to control and coordinate thesystem. The Gainspeed controller (1102) is operationally defined byFIGS. 12-15. The Gainspeed controller can be used, for example, toinstruct the edge router (1104) to look for a certain type or class oftraffic, and provide the proper priority or shaping for that class oftraffic.

Depending upon the system configuration, the edge router (1104) may ormay not be expected to manage the various cable modems. In someembodiments, the Gainspeed controller can be used to provide some or allparameters needed to appropriately configure the functionality of theedge router (1104), and deliver the desired level of service.

FIG. 12 shows a diagram of some of the more important communicationprotocols that go between the different entities or elements of thesystem. For example, FIG. 12 shows:

1) The bidirectional communication between the cable and the GainspeedEtherNode;

2) The bidirectional communication between the Gainspeed EtherNode andthe edge router;

3) The bidirectional communication between the edge router and theGainspeed controller;

4) The bidirectional communication and between the Gainspeed controllerand the cable operator servers or back office.

FIGS. 13-15 provide a further discussion of the protocols and interfacesbetween the operator servers, the Gainspeed controller(s) (1102), edgerouter(s) (1104), Gainspeed EtherNode(s)/DOFN (1106/300,304), and thehousehold cable modem (CM) (208) and CPE devices. Note again that thesefigures do double duty because in addition to showing a more detaileddescription of the various system communication protocols, the figuresalso serve to give an operational definition of the functions of theGainspeed controller and other devices. Here, an operational definitionof the functions performed by the operator servers (e.g. cable operatorservers), the edge router (e.g. Juniper Networks MX edge router), theGainspeed EtherNode, and the household cable modem and CPE devices isthus provided.

Note that the invention may be implemented in a stepwise manner, withmore and more functionality implemented as the cable operator desires.

For example, at the most basic demonstration level, the system can beimplemented to perform basic IPv4 forwarding, and not implement Qualityof Service (QoS) functionality. At the basic level, the system can alsoimplement Point to point (P2P) Ethernet private line (EPL) service forcable modems, but without functions such as VLAN ID re-write, and withno CoS re-marking of data packets. At the basic level, the system canalso implement Border Gateway Protocol (BGP) or Label DistributionProtocol (LDP) signaling on the MX or other edge router (1104).

At a higher level of functionality, the system may also implementservice attribute enforcement on the MX or other edge router (1104).This can include Quality of Service (QoS) policy (e.g. network facing,SF mapped), packet filters (e.g. standard, DOCSIS subscriber management)type filters. The system can also implement dynamic service attributeadjustments, and also provide the convenience of session tear-down whenthe cable modem(s) go offline. The system can also implement some basisstatistics export. This might include QoS policy, packet filters,Ethernet interface packet/byte counters, and the like.

At a still higher level of functionality, the system may also implementmore advanced functions, such as IPv6 support, packet cable, andmulticast support. The system can also implement Routing InformationProtocol (RIP) routes, dynamic service flow signaling, and more advancedstatistical reporting.

Thus to reiterate, in some embodiments, the system can be implemented inan incremental or step-wise manner, starting with basic IPv4 forwardingand P2P Level 2 VPN networking, and upgraded to implement additionalfunctions such as providing various quality of service (QoS) policies(e.g. network facing, SF mapped), various dynamic service attributeadjustments, ability to cope when the cable modems go off line withsession tear-down capability, and basic statistics export (e.g. QoSpolicy, packet filters, Ethernet interface packet/byte counters, and thelike. At a still higher step up, the system may additionally do otherfunctions such as IPv6, packet cable, and multicast support. The systemmay additionally implement RIP routs, dynamic service flow signaling,implement a fuller set of reporting statistics, and strive for highavailability.

FIG. 15 shows a further discussion of system architecture and functions.In particular it discusses the protocol operations in the invention'svirtual converged cable access platform.

The Motorola CCAP 101 white paper, shown in the appendix of prioritydocument U.S. provisional 61/870,226, and incorporated herein byreference, discusses repartitioning DOCSIS to various different elementsof the network. These are separate entities, such as a node, an edgerouter, back office, and control node(s).

Among other aspects, in some embodiments, the present invention canvirtualize many of the functions described in the Motorola CCAP 101white paper.

Thus in one embodiment, the invention may be either a system or a methodof operating an HFC cable network using a virtual converged cable accessplatform (1120) configured to relay data between at least one cablemodem (208) and at least one operator server (1100). This virtualconverged cable access platform will generally comprise at least onevirtual CCAP controller (1102), at least one edge router (1104), andplurality of digital optical fiber nodes (DOFN) (1106 and 300,304),connected to at least one set of neighborhood CATV cables (226) with atleast one CATV connected cable modem (208). The invention will generallyoperate by using the DOFN (1106/300,304) to detect the one or more cablemodem(s) (208), and transmit notification that a given cable modem hasbeen detected back through the optical fiber (222) and the edge router(1104) to the virtual CCAP controller (1102). The invention will in turnuse the virtual CCAP controller (1102) and the edge router (1104) todiscover and acknowledge the cable modem (see FIGS. 12 and 13 for moredetail).

The invention will also use the virtual CCAP controller (1102) and edgerouter (1104) to discover at least one operator server (1100), andfurther use the DOFN (1106/300,304) to relay data between the cablemodem(s) (208) over the RF portion of the CATV cable (226) and opticalfiber (222) to the one or more operator servers (1100) by way of theedge router (1104) as controlled by the virtual CCAP controller (1102).

The invention will further use the virtual CCAP controller (1102) totransmit cable service rules to the edge router (1104), and receiveacknowledgement of these service rules from the edge router (see FIG. 13for more detail). The amount and type of data subsequently relayedbetween the cable modem(s) (208) and the one or more operator servers(1100) is or will be controlled by these service rules.

Often these service rules can be at virtual local area network (VLAN)rewrite rules, password identification, password remote destination, orvarious CATV network Quality of Service rules. Here for example,depending on what level of service the user of cable modem (208) hascontracted for, different operator servers (1100), different content,and different speeds may be made available.

As previously discussed, often the virtual CCAP controller (1102) can beconfigured to interface with legacy operator servers or systems usingone or more protocols, such as the simple network management protocol(SNMP), internet protocol detail record (IPDR), packet cable multi-media(PCMM) protocol, Network Configuration Protocol (NETCONF), command lineinterface (CLI) protocol, or other protocol.

The virtual CCAP controller (1102) can also be configured to manage theprocess of bringing cable modem and customer premises equipment onlineto said HFC cable network. To help facilitate this process, and/or forother functions as well, the virtual CCAP controller (1102) can also beconfigured to implement and use dynamic host configuration (DHCP) relayand various edge router program interface protocols as well.

As previously discussed, the virtual CCAP controller (1102) willgenerally comprise at least one processor (often a plurality ofprocessors, which may be a mix of general purpose microprocessors andcustomized high performance processors with instruction sets optimizedfor these purposes), memory, suitable interfaces, and virtual CCAPsoftware configured to run on the controller's least one processor,direct the controller processor(s) to issue commands to the edge router(1104).

Some of these commands can be commands to direct the edge router tointerface with legacy operator servers or systems. Here it may be usefulto use various protocols, such as the previously discussed simplenetwork management protocol (SNMP), internet protocol detail record(IPDR), packet cable multi-media (PCMM), Network Configuration Protocol(NETCONF), command line interface (CLI) protocol or other protocol. Thecontroller's software commands will generally also work with the edgerouter (1104) to manage the process of bringing the cable modem (208)and other customer premises equipment online to the HFC cable network,as well as to further implement dynamic host configuration (DHCP) relayand other edge router program interface protocols.

The edge router (1104) will often be configured (often with commandsfrom controller 1102) to handle all level 3+ network layer protocols,including packet forwarding, and routing through intermediate routers.The edge router (1104) will often also be further configured toimplement router control plane addressing. Here various protocols suchas the label distribution protocol (LDP), border gateway protocol (BGP),Intermediate System to Intermediate System (ISIS) protocol, and openshortest path first (OSPF) protocol may be used. In particular, thecontroller (1102) will often configure the edge router (1104) toimplement various level 3 packet processing functions, such asmultiprotocol label switching IP forwarding, subscriber quality ofservice (QoS), packet filters, and virtual local area network (VLAN)manipulation.

The invention's virtual head end generally relies upon capable DOFN(300,304/1106). As previously discussed, these DOFN will generally beconfigured to manage a plurality of Cable Radiofrequency and DOCSISfunctions, such as RF modulation, implementation of suitable CATV cableand optical fiber MAC/PHY functionally, data encryption, and variousdata scheduling functions. These DOFN will often be connected to theCATV RF cable at one end, and to the optical fiber (222) whicheventually (often by various intermediate switches and sections that arenot shown) connect to the edge router (1104).

Thus often the invention will implement its various systems and methodsby using the virtual CCAP controller(s) (1102) and edge router(s) (1104)to create a virtual head end (1120) that in turn connects to andcontrols the rest of the HFC cable network (i.e. least one optical fibercable to at least one digital optical fiber node (DOFN) that isconnected to at least one set of neighborhood CATV cables). Theinvention can operate to transmit, for example, various legacy CATVdownstream QAM channels, as desired, by transmitting at least onedownstream QAM channel over the optical fiber as a plurality of QAMconstellation symbols. This can be done digitally by encapsulating theseQAM constellation symbols into a plurality of Ethernet frames or otherdigital transmission format frames, and digitally transmitting thisplurality of Ethernet frames or other digital transmission format framesover the optical fiber (222). Note that QAM symbol encapsulation orother digital transmission format can be either done in real time by oneor more operator servers (1100) or converters (399), or alternativelythis QAM symbol encapsulation or other digital transmission format canbe done in non-real time, and simply saved on the operator servers(1100) for use as needed for later transmission.

Once the digital transmission is handled by edge router (1104), ascommanded by controller (1102), and is transmitted over the opticalfiber (222) to the DOFN (1106/300,304) (often as Ethernet frames orother digital transmission format), the DOFN can then receive thisplurality of Ethernet frames or other digital transmission formatclaims. The DOFN can then extract the downstream QAM constellationsymbols, and use the downstream video QAM constellation symbols tomodulate at least one DOFN QAM modulator (607), (712), thus producingdownstream QAM RF signals. The DOFN can then transmit these DOFNgenerated downstream QAM modulated RF signals further downstream oversaid at least one set of neighborhood CATV cables (226).

As previously discussed, many different types of QAM channels may betransmitted by this type of process, including video QAM channels, videoEdge-QAM channels, or IP-QAM channels. See FIG. 7 for some specificexamples.

In other embodiments, and also as discussed in FIG. 7 and elsewhere,these methods may also be used to transmit other types of downstreamdata, such as National Television System Committee (NTSC) or OrthogonalFrequency Division Multiplexing (OFDM) RF channels. This can be doneusing operator servers (1100) and or converters (399) to furtherdigitally process the data prior to the data then being processed by thecontroller (1102) and edge router (1104), and being transmitted over theoptical fiber (222).

Here again, the process will generally comprise, either in real time, oron a non-real time basis (e.g. using a converter 399, or storing thedata in an operator server 1100 after digital sampling), digitallysampling the NTSC or OFDM RF channels, thus producing a plurality ofdigitized waveform data, and again encapsulating this digitized waveformdata into a plurality of digitized waveform data containing Ethernetframes or other digital transmission frames. This can then, with the aidof controller (1102) and edge router (1104) digitally transmitted thedata downstream over the optical fiber (222). Once at the DOFN(1106/300,304), the DOFN can be used to receive the digitized waveformdata containing Ethernet frames or other digital transmission frames,extract this plurality of digitized waveform data, and use thisplurality of digitized waveform data to drive at least one digital toanalog converter, thus producing downstream NTSC or OFDM RF channels(see FIG. 7 and elsewhere for details). These DOFN generated NTSC orOFDM RF signals are then transmitted further downstream, in RF form,over the neighborhood CATV cables (206) to the subscriber's equipment.

Similarly, when the downstream data comprises Orthogonal FrequencyDivision Multiplexing (OFDM) RF channels, the system can operate byeither in real time or non-real time demodulating the OFDM RF channels,producing a plurality of OFDM symbols, and encapsulating this pluralityof OFDM symbols into a plurality of OFDM symbol carrying Ethernet framesor other digital transmission frames. As before, the edge router (1104),as commanded by the controller (1102), can digitally transmit thisinformation over the optical fiber (222) to the DOFN (1106/300,304),where again the DOFN can extract the information, us it to drive atleast one OFDM RF modulator, and transmit the resulting OFDM RF signalsfurther downstream over the neighborhood CATV cables (226).

Going upstream, the process essentially can be run in reverse. Forexample, the invention's systems and methods may also be used to, overthe optical fiber, digitally transmit upstream RF QAM channel dataoriginating from at least one CATV cable (226) connected cable modem(208) or other neighborhood CATV cable connected devices. Here the DOFN(1106/300,304) will receive this upstream RF QAM channel data, willdemodulate least one upstream RF QAM channel into a plurality ofupstream QAM constellation symbols. This is shown in more detail in FIG.7 (605). The DOFN will then encapsulate this plurality of upstream QAMconstellation symbols into a plurality of Ethernet frames or otherdigital transmission format frames, and use the optical fiber (222) todigitally transmit said plurality of Ethernet frames or other digitaltransmission format frames upstream to said virtual head end. There theedge router (1104) and Gainspeed controller (1102) can then interpretthe upstream information or further route this upstream information asappropriate. This process is shown in more detail in FIGS. 12-13 and 15.

Similarly, the invention's methods may also be used to digitallytransmit upstream RF OFDM channel data (again typically originating fromthe cable modem (208) or other cable connected devices) over the opticalfiber (222) as well. Here again, the DOFN can receive upstream RF OFDMchannel data, and demodulate this into a plurality of upstream OFDMsymbols. These OFDM symbols can then also be encapsulating into aplurality of Ethernet frames or other digital transmission formatframes, and transmitted upstream, over optical fiber (222), to thevirtual head end (1120) where the same type of interpretation androuting process can occur.

In the same manner, the invention's methods may also be used todigitally transmit upstream RF channel data. Here the DOFN, uponreceiving the upstream RF channel data, can digitally sample the RFchannel data (see FIG. 7 (601)), producing a plurality of digitizedwaveform data. This can also be encapsulated into a plurality ofEthernet frames or other digital transmission frames, and alsotransmitted upstream, over optical fiber (222) to the virtual head end(1120) where again this data may be interpreted and routed asappropriate.

Note that often upstream data may consist, at least in part; of varioustypes of instructions for the HFC head end (for example, see FIGS.12-15). Here to interpret these instructions, the virtual head end,usually using the controller (1102) and controller software (e.g.virtual CCAP controller software) can, while still operating in thedigital domain, interpret these various instructions and act on themwithout the need to reconstitute the original RF waveforms originallyused to transmit RF upstream data over the cable (226), other types ofupstream data, such as DOCSIS IP data, and the like, can also be handledby the controller (1102) and edge router (1104) and directed to thedesired destination, again keeping entirely to the digital domain duringthis process. Thus the virtual head end (1120) can operate entirely inthe digital domain, as desired.

The invention may be used either to upgrade a legacy Hybrid Fiber Cable(legacy HFC) system (i.e. a system previously configured to transmitdata downstream over said optical fiber using analog optical QAMwaveforms), or to produce a brand new (non-legacy) HFC system, asdesired.

In the case where it is desired to upgrade a legacy HFC system, thenthis legacy system will usually comprise a legacy head end (202)configured to produce downstream RF QAM waveforms, as well as a legacyfiber optic transmitter system configured to transduce said RF QAMwaveforms into downstream analog optical QAM waveforms such as (120),and send these analog optical QAM waveforms downstream over the opticalfiber (222) to at least one legacy optical fiber node such as (204).This legacy optical fiber node (204) will generally be configured toreceive these downstream analog optical QAM waveforms (120) andtransduce said analog optical QAM waveforms into RF QAM waveforms (110),and transmit these RF QAM waveforms downstream over at least one set ofneighborhood CATV cables (226).

In this case, this legacy HFC system may be upgraded by replacing thelegacy head end (202) with a virtual head end (1120), and also replacingthe legacy optical fiber nodes (204) with various DOFN (1106/300,304).Backward compatibility with legacy cable modems (208) and otherequipment can be maintained by, for example, further configuring thevirtual head end (1120) and at least one operator server (1100) totransmit at least one downstream RF QAM channel over the optical fiber(222) as a plurality of QAM constellation symbols encapsulated into aplurality of Ethernet frames or other digital transmission format framesusing a digital optical transmission method.

Of course there is no requirement that the HFC system be a legacysystem. The invention's methods may also be used to create an entirelynew HFC system by simply using the invention's virtual head end (1120)and DOFN (1106/300,304) from the beginning of the HFC cable constructionprocess, without the need to swap out legacy equipment.

1. A method of operating an HFC cable network using a virtual convergedcable access platform configured to relay data between at least onecable modem and operator server; said virtual converged cable accessplatform comprising at least one virtual CCAP controller, at least oneedge router, and plurality of digital optical fiber nodes (DOFN),connected to at least one set of neighborhood CATV cables with at leastone CATV connected cable modem, said method comprising: using said DOFNto detect said cable modem, and transmit notification of said cablemodem detection via said edge router to said virtual CCAP controller,and using said virtual CCAP controller and said edge router to createand acknowledge said cable modem; using said virtual CCAP controller andedge router to discover at least one operator server, and further usingsaid DOFN to relay data between said cable modem and said operatorservers by way of said edge router and said virtual CCAP controller;further using said virtual CCAP controller to transmit cable servicerules to said edge router, and receive acknowledgement of said servicerules from said edge router; wherein the amount and type of data relayedbetween said cable modem and said operator servers is controlled by saidservice rules.
 2. The method of claim 1, wherein said service rulescomprise at least one of VLAN rewrite rules, password identification,password remote destination, or Quality of service rules.
 3. The methodof claim 1, wherein said virtual CCAP controller is configured tointerface with legacy operator servers or systems using at least one ofsimple network management protocol (SNMP), internet protocol detailrecord (IPDR), packet cable multimedia (PCMM), Network ConfigurationProtocol (NETCONF), or command line interface (CLI) protocol.
 4. Themethod of claim 3, wherein said virtual CCAP controller is furtherconfigured to manage the process of bringing cable modem and customerpremises equipment online to said HFC cable network, and wherein saidvirtual CCAP controller further implements dynamic host configuration(DHCP) relay and edge router program interface protocols.
 5. The methodof claim 3, wherein said virtual CCAP controller comprises at least oneprocessor, memory, and virtual CCAP software configured to run on saidat least one processor, and to issue commands to said edge router toeither: 1: interface with legacy operator servers or systems using atleast one of simple network management protocol (SNMP), internetprotocol detail record (IPDR), packet cable multimedia (PCMM), NetworkConfiguration Protocol (NETCONF), or command line interface (CLI)protocol; or 2: manage the process of bringing cable modem and customerpremises equipment online to said HFC cable network, and to furtherimplement dynamic host configuration (DHCP) relay and edge routerprogram interface protocols.
 6. The method of claim 1, wherein said edgerouter is further configured to handle all level 3+ network layerprotocols, including packet forwarding, and routing through intermediaterouters.
 7. The method of claim 1, wherein said edge router is furtherconfigured to implement router control plane addressing including atleast one of label distribution protocol (LDP), border gateway protocol(BGP), Intermediate System to Intermediate System (ISIS) protocol, openshortest path first (OSPF) protocol; and wherein said edge router isfurther configured to implement at least some level 3 packet processingfunctions including multiprotocol label switching IP forwarding,subscriber quality of service, packet filters, and virtual local areanetwork (VLAN) manipulation.
 8. The method of claim 1, wherein said DOFNis configured to manage a plurality of Cable Radiofrequency and DOCSISfunctions, said functions comprising RF modulation, MAC/PHY, Encryption,and Scheduling.
 9. The method of claim 1, wherein said at least one edgerouter is connected to said at least one DOFN by at least one opticalfiber.
 10. The method of claim 1, wherein said method of operating anHFC cable network further comprises using said virtual CCAP controllerand at least one edge router to create a virtual head end; said HFCcable network further comprises at least a virtual head end connected byat least one optical fiber cable to at least one digital optical fibernode (DOFN) that is connected to at least one set of neighborhood CATVcables, and wherein said data comprises downstream QAM channels; saidmethod further comprising: transmitting at least one downstream QAMchannel over the optical fiber as a plurality of QAM constellationsymbols by encapsulating said QAM constellation symbols into a pluralityof Ethernet frames or other digital transmission format frames, anddigitally transmitting said plurality of Ethernet frames or otherdigital transmission format frames over said optical fiber; using saidDOFN to receive said plurality of Ethernet frames or other digitaltransmission format claims, extract said downstream QAM constellationsymbols, and use said downstream video QAM constellation symbols tomodulate at least one DOFN QAM modulator, thus producing downstream QAMRF signals, and transmitting said DOFN generated downstream QAMmodulated RF signals further downstream over said at least one set ofneighborhood CATV cables.
 11. The method of claim 10, wherein said QAMchannels comprise either video QAM channels, video Edge-QAM channels, orIP-QAM channels.
 12. The method of claim 10, wherein said downstreamdata further comprises National Television System Committee (NTSC) orOrthogonal Frequency Division Multiplexing (OFDM) RF channels, andfurther digitally transmitting said data over said optical fiber by:digitally sampling said NTSC or OFDM RF channels, producing a pluralityof digitized waveform data, encapsulating said digitized waveform datainto a plurality of digitized waveform data containing Ethernet framesor other digital transmission frames, and digitally transmitting saidplurality of digitized waveform data containing Ethernet frames or otherdigital transmission frames downstream over said optical fiber; usingsaid DOFN to receive said plurality of digitized waveform datacontaining Ethernet frames or other digital transmission frames, extractsaid plurality of digitized waveform data, and use said plurality ofdigitized waveform data to drive at least one digital to analogconverter, thus producing downstream NTSC or OFDM RF channels; andfurther transmitting said DOFN generated NTSC or OFDM RF signals furtherdownstream over said at least one set of neighborhood CATV cables. 13.The method of claim 10, wherein said downstream data further comprisesOrthogonal Frequency Division Multiplexing (OFDM) RF channels andfurther digitally transmitting said data over said optical fiber by:demodulating said OFDM RF channels, producing a plurality of OFDMsymbols, encapsulating said plurality of OFDM symbols into a pluralityof OFDM symbol carrying Ethernet frames or other digital transmissionframes, and digitally transmitting said OFDM symbol carrying Ethernetframes or other digital transmission frames downstream over said opticalfiber; using said DOFN to receive said plurality of OFDM symbol carryingEthernet frames or other digital transmission frames, extract saidplurality of OFDM symbols, and using said plurality of OFDM symbols todrive at least one OFDM RF modulator, thus producing downstream OFDM RFchannels; and further transmitting said DOFN produced OFDM RF signalsfurther downstream over said at least one set of neighborhood CATVcables.
 14. The method of claim 10, further used to digitally transmitupstream RF QAM channel data originating from at least one cable modemor other neighborhood CATV cable connected devices, over said opticalfiber, by: at said DOFN, receiving said upstream RF QAM channel data,and demodulating said at least one upstream RF QAM channel into aplurality of upstream QAM constellation symbols; encapsulating saidplurality of upstream QAM constellation symbols into a plurality ofEthernet frames or other digital transmission format frames; and usingsaid optical fiber to digitally transmit said plurality of Ethernetframes or other digital transmission format frames upstream to saidvirtual head end.
 15. The method of claim 10, further used to digitallytransmit upstream RF OFDM channel data, originating from at least onecable modem or other neighborhood CATV cable connected devices, oversaid optical fiber, by: at said DOFN, receiving said upstream RF OFDMchannel data, and demodulating said at least one upstream RF OFDMchannel into a plurality of upstream OFDM symbols; encapsulating saidplurality of upstream OFDM symbols into a plurality of Ethernet framesor other digital transmission format frames; and using said opticalfiber to digitally transmit said plurality of Ethernet frames or otherdigital transmission format frames to upstream said virtual head end.16. The method of claim 10, further used to digitally transmit upstreamRF channel data, and further digitally transmitting said data over saidoptical fiber by: at said DOFN, receiving said upstream RF channel data,digitally sampling said RF channel data producing a plurality ofdigitized waveform data; encapsulating said digitized waveform data intoa plurality of Ethernet frames or other digital transmission frames; andusing said optical fiber to digitally transmit said plurality ofEthernet frames or other digital transmission frames upstream to saidvirtual head end.
 17. The method of claim 10, used to upgrade a legacyHybrid Fiber Cable (legacy HFC) system previously configured to transmitdata downstream over said optical fiber using analog optical QAMwaveforms, said legacy HFC system comprising: a head end configured toproduce downstream RF QAM waveforms; a legacy fiber optic transmittersystem configured to transduce said RF QAM waveforms into downstreamanalog optical QAM waveforms; wherein said optical fiber is configuredto transmit said analog optical QAM waveforms downstream to at least onelegacy optical fiber node; wherein said at least one legacy opticalfiber node is configured to receive said downstream analog optical QAMwaveforms, transduce said analog optical QAM waveforms into RF QAMwaveforms, and transmit said RF QAM waveforms downstream over said atleast one set of neighborhood CATV cables; said method furthercomprising: replacing said head end with said virtual head end;replacing said at least one legacy optical fiber node with at least oneDOFN; wherein said virtual head end and at least one operator server areconfigured to transmit at least one downstream RF QAM channel over saidoptical fiber as a plurality of QAM constellation symbols encapsulatedinto a plurality of Ethernet frames or other digital transmission formatframes using a digital optical transmission method.